It is expected that errno be passed to strerror(). This also cleans
this part of code from using libbpf_get_error().
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>
Acked-by: Yonghong Song <yhs@fb.com>
Suggested-by: Quentin Monnet <quentin@isovalent.com>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20221120112515.38165-4-sahid.ferdjaoui@industrialdiscipline.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
There is no reasons to keep PTR_ERR() when kern_btf=NULL, let's just
return 0.
This also cleans this part of code from using libbpf_get_error().
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>
Acked-by: Yonghong Song <yhs@fb.com>
Suggested-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20221120112515.38165-3-sahid.ferdjaoui@industrialdiscipline.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Yonghong Song says:
====================
Currenty, a non-tracing bpf program typically has a single 'context' argument
with predefined uapi struct type. Following these uapi struct, user is able
to access other fields defined in uapi header. Inside the kernel, the
user-seen 'context' argument is replaced with 'kernel context' (or 'kctx'
in short) which can access more information than what uapi header provides.
To access other info not in uapi header, people typically do two things:
(1). extend uapi to access more fields rooted from 'context'.
(2). use bpf_probe_read_kernl() helper to read particular field based on
kctx.
Using (1) needs uapi change and using (2) makes code more complex since
direct memory access is not allowed.
There are already a few instances trying to access more information from
kctx:
. trying to access some fields from perf_event kctx ([1]).
. trying to access some fields from xdp kctx ([2]).
This patch set tried to allow direct memory access for kctx fields
by introducing bpf_cast_to_kern_ctx() kfunc.
Martin mentioned a use case like type casting below:
#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
basically a 'unsigned char *" casted to 'struct skb_shared_info *'. This patch
set tries to support such a use case as well with bpf_rdonly_cast().
For the patch series, Patch 1 added support for a kfunc available to all
prog types. Patch 2 added bpf_cast_to_kern_ctx() kfunc. Patch 3 added
bpf_rdonly_cast() kfunc. Patch 4 added a few positive and negative tests.
[1] https://lore.kernel.org/bpf/ad15b398-9069-4a0e-48cb-4bb651ec3088@meta.com/
[2] https://lore.kernel.org/bpf/20221109215242.1279993-1-john.fastabend@gmail.com/
Changelog:
v3 -> v4:
- remove unnecessary bpf_ctx_convert.t error checking
- add and use meta.ret_btf_id instead of meta.arg_constant.value for
bpf_cast_to_kern_ctx().
- add PTR_TRUSTED to the return PTR_TO_BTF_ID type for bpf_cast_to_kern_ctx().
v2 -> v3:
- rebase on top of bpf-next (for merging conflicts)
- add the selftest to s390x deny list
rfcv1 -> v2:
- break original one kfunc into two.
- add missing error checks and error logs.
- adapt to the new conventions in
https://lore.kernel.org/all/20221118015614.2013203-1-memxor@gmail.com/
for example, with __ign and __k suffix.
- added support in fixup_kfunc_call() to replace kfunc calls with a single mov.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Three tests are added. One is from John Fastabend ({1]) which tests
tracing style access for xdp program from the kernel ctx.
Another is a tc test to test both kernel ctx tracing style access
and explicit non-ctx type cast. The third one is for negative tests
including two tests, a tp_bpf test where the bpf_rdonly_cast()
returns a untrusted ptr which cannot be used as helper argument,
and a tracepoint test where the kernel ctx is a u64.
Also added the test to DENYLIST.s390x since s390 does not currently
support calling kernel functions in JIT mode.
[1] https://lore.kernel.org/bpf/20221109215242.1279993-1-john.fastabend@gmail.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195442.3114844-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Implement bpf_rdonly_cast() which tries to cast the object
to a specified type. This tries to support use case like below:
#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
where skb_end_pointer(SKB) is a 'unsigned char *' and needs to
be casted to 'struct skb_shared_info *'.
The signature of bpf_rdonly_cast() looks like
void *bpf_rdonly_cast(void *obj, __u32 btf_id)
The function returns the same 'obj' but with PTR_TO_BTF_ID with
btf_id. The verifier will ensure btf_id being a struct type.
Since the supported type cast may not reflect what the 'obj'
represents, the returned btf_id is marked as PTR_UNTRUSTED, so
the return value and subsequent pointer chasing cannot be
used as helper/kfunc arguments.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195437.3114585-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Implement bpf_cast_to_kern_ctx() kfunc which does a type cast
of a uapi ctx object to the corresponding kernel ctx. Previously
if users want to access some data available in kctx but not
in uapi ctx, bpf_probe_read_kernel() helper is needed.
The introduction of bpf_cast_to_kern_ctx() allows direct
memory access which makes code simpler and easier to understand.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195432.3113982-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Later on, we will introduce kfuncs bpf_cast_to_kern_ctx() and
bpf_rdonly_cast() which apply to all program types. Currently kfunc set
only supports individual prog types. This patch added support for kfunc
applying to all program types.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195426.3113828-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
In the unlikely event that bpf_global_ma is not correctly initialized,
instead of checking the boolean everytime bpf_obj_new_impl is called,
simply check it while loading the program and return an error if
bpf_global_ma_set is false.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221120212610.2361700-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
- Fix possible NULL pointer dereference on trace_event_file in kprobe_event_gen_test_exit()
- Fix NULL pointer dereference for trace_array in kprobe_event_gen_test_exit()
- Fix memory leak of filter string for eprobes
- Fix a possible memory leak in rethook_alloc()
- Skip clearing aggrprobe's post_handler in kprobe-on-ftrace case
which can cause a possible use-after-free
- Fix warning in eprobe filter creation
- Fix eprobe filter creation as it picked the wrong event for the fields
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Merge tag 'trace-probes-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing/probes fixes from Steven Rostedt:
- Fix possible NULL pointer dereference on trace_event_file in
kprobe_event_gen_test_exit()
- Fix NULL pointer dereference for trace_array in
kprobe_event_gen_test_exit()
- Fix memory leak of filter string for eprobes
- Fix a possible memory leak in rethook_alloc()
- Skip clearing aggrprobe's post_handler in kprobe-on-ftrace case which
can cause a possible use-after-free
- Fix warning in eprobe filter creation
- Fix eprobe filter creation as it picked the wrong event for the
fields
* tag 'trace-probes-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing/eprobe: Fix eprobe filter to make a filter correctly
tracing/eprobe: Fix warning in filter creation
kprobes: Skip clearing aggrprobe's post_handler in kprobe-on-ftrace case
rethook: fix a potential memleak in rethook_alloc()
tracing/eprobe: Fix memory leak of filter string
tracing: kprobe: Fix potential null-ptr-deref on trace_array in kprobe_event_gen_test_exit()
tracing: kprobe: Fix potential null-ptr-deref on trace_event_file in kprobe_event_gen_test_exit()
- Fix polling to block on watermark like the reads do, as user space
applications get confused when the select says read is available, and then
the read blocks.
- Fix accounting of ring buffer dropped pages as it is what is used to
determine if the buffer is empty or not.
- Fix memory leak in tracing_read_pipe()
- Fix struct trace_array warning about being declared in parameters
- Fix accounting of ftrace pages used in output at start up.
- Fix allocation of dyn_ftrace pages by subtracting one from order instead of
diving it by 2
- Static analyzer found a case were a pointer being used outside of a NULL
check. (rb_head_page_deactivate())
- Fix possible NULL pointer dereference if kstrdup() fails in ftrace_add_mod()
- Fix memory leak in test_gen_synth_cmd() and test_empty_synth_event()
- Fix bad pointer dereference in register_synth_event() on error path.
- Remove unused __bad_type_size() method
- Fix possible NULL pointer dereference of entry in list 'tr->err_log'
- Fix NULL pointer deference race if eprobe is called before the event setup
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Merge tag 'trace-v6.1-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing fixes from Steven Rostedt:
- Fix polling to block on watermark like the reads do, as user space
applications get confused when the select says read is available, and
then the read blocks
- Fix accounting of ring buffer dropped pages as it is what is used to
determine if the buffer is empty or not
- Fix memory leak in tracing_read_pipe()
- Fix struct trace_array warning about being declared in parameters
- Fix accounting of ftrace pages used in output at start up.
- Fix allocation of dyn_ftrace pages by subtracting one from order
instead of diving it by 2
- Static analyzer found a case were a pointer being used outside of a
NULL check (rb_head_page_deactivate())
- Fix possible NULL pointer dereference if kstrdup() fails in
ftrace_add_mod()
- Fix memory leak in test_gen_synth_cmd() and test_empty_synth_event()
- Fix bad pointer dereference in register_synth_event() on error path
- Remove unused __bad_type_size() method
- Fix possible NULL pointer dereference of entry in list 'tr->err_log'
- Fix NULL pointer deference race if eprobe is called before the event
setup
* tag 'trace-v6.1-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing: Fix race where eprobes can be called before the event
tracing: Fix potential null-pointer-access of entry in list 'tr->err_log'
tracing: Remove unused __bad_type_size() method
tracing: Fix wild-memory-access in register_synth_event()
tracing: Fix memory leak in test_gen_synth_cmd() and test_empty_synth_event()
ftrace: Fix null pointer dereference in ftrace_add_mod()
ring_buffer: Do not deactivate non-existant pages
ftrace: Optimize the allocation for mcount entries
ftrace: Fix the possible incorrect kernel message
tracing: Fix warning on variable 'struct trace_array'
tracing: Fix memory leak in tracing_read_pipe()
ring-buffer: Include dropped pages in counting dirty patches
tracing/ring-buffer: Have polling block on watermark
The IXP4xx is just using the device tree now, only keep the
static UART map if and only if we are debugging.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Commit c83227a5d0 ("irq/gpio: ixp4xx: Drop boardfile probe path") and
commit 155e4306107f ("clocksource/drivers/ixp4xx: Drop boardfile probe
path") remove files include/linux/irqchip/irq-ixp4xx.h and
include/linux/platform_data/timer-ixp4xx.h, but miss to adjust MAINTAINERS.
Hence, ./scripts/get_maintainer.pl --self-test=patterns complains about
broken references.
Remove file entries for those files in ARM/INTEL IXP4XX ARM ARCHITECTURE.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20221115123102.22732-1-lukas.bulwahn@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
- Use dynamic GPIO base on combined pincctrl/gpio controllers on
SH/R-Mobile SoCs,
- Miscellaneous improvements.
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Merge tag 'renesas-pinctrl-for-v6.2-tag1' of git://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers into devel
pinctrl: renesas: Updates for v6.2
- Use dynamic GPIO base on combined pincctrl/gpio controllers on
SH/R-Mobile SoCs,
- Miscellaneous improvements.
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
.probe_new() doesn't get the i2c_device_id * parameter, so determine
that explicitly in the probe function.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The probe function doesn't make use of the i2c_device_id * parameter so it
can be trivially converted.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Merge immutable branch adding 'i2c_client_get_device_id()' function,
so that drivers can easily be converted to use i2c_driver::probe_new.
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
The flag that tells the event to call its triggers after reading the event
is set for eprobes after the eprobe is enabled. This leads to a race where
the eprobe may be triggered at the beginning of the event where the record
information is NULL. The eprobe then dereferences the NULL record causing
a NULL kernel pointer bug.
Test for a NULL record to keep this from happening.
Link: https://lore.kernel.org/linux-trace-kernel/20221116192552.1066630-1-rafaelmendsr@gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20221117214249.2addbe10@gandalf.local.home
Cc: Linux Trace Kernel <linux-trace-kernel@vger.kernel.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 7491e2c442 ("tracing: Add a probe that attaches to trace events")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reported-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
fpregs lock disables preemption on RT but fpu_inherit_perms() does
spin_lock_irq(), which, on RT, uses rtmutexes and they need to be
preemptible.
- Check the page offset and the length of the data supplied by userspace
for overflow when specifying a set of pages to add to an SGX enclave
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Merge tag 'x86_urgent_for_v6.1_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Borislav Petkov:
- Do not hold fpregs lock when inheriting FPU permissions because the
fpregs lock disables preemption on RT but fpu_inherit_perms() does
spin_lock_irq(), which, on RT, uses rtmutexes and they need to be
preemptible.
- Check the page offset and the length of the data supplied by
userspace for overflow when specifying a set of pages to add to an
SGX enclave
* tag 'x86_urgent_for_v6.1_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/fpu: Drop fpregs lock before inheriting FPU permissions
x86/sgx: Add overflow check in sgx_validate_offset_length()
misunderstanding whether the task holds rq->lock or not
- Prevent processes from getting killed when using deprecated or unknown
rseq ABI flags in order to be able to fuzz the rseq() syscall with
syzkaller
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Merge tag 'sched_urgent_for_v6.1_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Borislav Petkov:
- Fix a small race on the task's exit path where there's a
misunderstanding whether the task holds rq->lock or not
- Prevent processes from getting killed when using deprecated or
unknown rseq ABI flags in order to be able to fuzz the rseq() syscall
with syzkaller
* tag 'sched_urgent_for_v6.1_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched: Fix race in task_call_func()
rseq: Use pr_warn_once() when deprecated/unknown ABI flags are encountered
for more than 4K
- Fix a NULL ptr dereference which can happen after an NMI interferes
with the event enabling dance in amd_pmu_enable_all()
- Free the events array too when freeing uncore contexts on CPU online,
thereby fixing a memory leak
- Improve the pending SIGTRAP check
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Merge tag 'perf_urgent_for_v6.1_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Borislav Petkov:
- Fix an intel PT erratum where CPUs do not support single range output
for more than 4K
- Fix a NULL ptr dereference which can happen after an NMI interferes
with the event enabling dance in amd_pmu_enable_all()
- Free the events array too when freeing uncore contexts on CPU online,
thereby fixing a memory leak
- Improve the pending SIGTRAP check
* tag 'perf_urgent_for_v6.1_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/intel/pt: Fix sampling using single range output
perf/x86/amd: Fix crash due to race between amd_pmu_enable_all, perf NMI and throttling
perf/x86/amd/uncore: Fix memory leak for events array
perf: Improve missing SIGTRAP checking
- Fix writable sections being moved into the rodata region.
Thanks to: Nicholas Piggin, Christophe Leroy.
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Merge tag 'powerpc-6.1-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
Pull powerpc fix from Michael Ellerman:
- Fix writable sections being moved into the rodata region.
Thanks to Nicholas Piggin and Christophe Leroy.
* tag 'powerpc-6.1-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc: Fix writable sections being moved into the rodata region
David Vernet says:
====================
Now that BPF supports adding new kernel functions with kfuncs, and
storing kernel objects in maps with kptrs, we can add a set of kfuncs
which allow struct task_struct objects to be stored in maps as
referenced kptrs.
The possible use cases for doing this are plentiful. During tracing,
for example, it would be useful to be able to collect some tasks that
performed a certain operation, and then periodically summarize who they
are, which cgroup they're in, how much CPU time they've utilized, etc.
Doing this now would require storing the tasks' pids along with some
relevant data to be exported to user space, and later associating the
pids to tasks in other event handlers where the data is recorded.
Another useful by-product of this is that it allows a program to pin a
task in a BPF program, and by proxy therefore also e.g. pin its task
local storage.
In order to support this, we'll need to expand KF_TRUSTED_ARGS to
support receiving trusted, non-refcounted pointers. It currently only
supports either PTR_TO_CTX pointers, or refcounted pointers. What this
means in terms of the implementation is that check_kfunc_args() would
have to also check for the PTR_TRUSTED or MEM_ALLOC type modifiers when
determining if a trusted KF_ARG_PTR_TO_ALLOC_BTF_ID or
KF_ARG_PTR_TO_BTF_ID pointer requires a refcount.
Note that PTR_UNTRUSTED is insufficient for this purpose, as it does not
cover all of the possible types of potentially unsafe pointers. For
example, a pointer obtained from walking a struct is not PTR_UNTRUSTED.
To account for this and enable us to expand KF_TRUSTED_ARGS to include
allow-listed arguments such as those passed by the kernel to tracepoints
and struct_ops callbacks, this patch set also introduces a new
PTR_TRUSTED type flag modifier which records if a pointer was obtained
passed from the kernel in a trusted context.
Currently, both PTR_TRUSTED and MEM_ALLOC are used to imply that a
pointer is trusted. Longer term, PTR_TRUSTED should be the sole source
of truth for whether a pointer is trusted. This requires us to set
PTR_TRUSTED when appropriate (e.g. when setting MEM_ALLOC), and unset it
when appropriate (e.g. when setting PTR_UNTRUSTED). We don't do that in
this patch, as we need to do more clean up before this can be done in a
clear and well-defined manner.
In closing, this patch set:
1. Adds the new PTR_TRUSTED register type modifier flag, and updates the
verifier and existing selftests accordingly. Also expands
KF_TRUSTED_ARGS to also include trusted pointers that were not obtained
from walking structs.
2. Adds a new set of kfuncs that allows struct task_struct* objects to be
used as kptrs.
3. Adds a new selftest suite to validate these new task kfuncs.
---
Changelog:
v8 -> v9:
- Moved check for release register back to where we check for
!PTR_TO_BTF_ID || socket. Change the verifier log message to
reflect really what's being tested (the presence of unsafe
modifiers) (Alexei)
- Fix verifier_test error tests to reflect above changes
- Remove unneeded parens around bitwise operator checks (Alexei)
- Move updates to reg_type_str() which allow multiple type modifiers
to be present in the prefix string, to a separate patch (Alexei)
- Increase TYPE_STR_BUF_LEN size to 128 to reflect larger prefix size
in reg_type_str().
v7 -> v8:
- Rebased onto Kumar's latest patch set which, adds a new MEM_ALLOC reg
type modifier for bpf_obj_new() calls.
- Added comments to bpf_task_kptr_get() describing some of the subtle
races we're protecting against (Alexei and John)
- Slightly rework process_kf_arg_ptr_to_btf_id(), and add a new
reg_has_unsafe_modifiers() function which validates that a register
containing a kfunc release arg doesn't have unsafe modifiers. Note
that this is slightly different than the check for KF_TRUSTED_ARGS.
An alternative here would be to treat KF_RELEASE as implicitly
requiring KF_TRUSTED_ARGS.
- Export inline bpf_type_has_unsafe_modifiers() function from
bpf_verifier.h so that it can be used from bpf_tcp_ca.c. Eventually this
function should likely be changed to bpf_type_is_trusted(), once
PTR_TRUSTED is the real source of truth.
v6 -> v7:
- Removed the PTR_WALKED type modifier, and instead define a new
PTR_TRUSTED type modifier which is set on registers containing
pointers passed from trusted contexts (i.e. as tracepoint or
struct_ops callback args) (Alexei)
- Remove the new KF_OWNED_ARGS kfunc flag. This can be accomplished
by defining a new type that wraps an existing type, such as with
struct nf_conn___init (Alexei)
- Add a test_task_current_acquire_release testcase which verifies we can
acquire a task struct returned from bpf_get_current_task_btf().
- Make bpf_task_acquire() no longer return NULL, as it can no longer be
called with a NULL task.
- Removed unnecessary is_test_kfunc_task() checks from failure
testcases.
v5 -> v6:
- Add a new KF_OWNED_ARGS kfunc flag which may be used by kfuncs to
express that they require trusted, refcounted args (Kumar)
- Rename PTR_NESTED -> PTR_WALKED in the verifier (Kumar)
- Convert reg_type_str() prefixes to use snprintf() instead of strncpy()
(Kumar)
- Add PTR_TO_BTF_ID | PTR_WALKED to missing struct btf_reg_type
instances -- specifically btf_id_sock_common_types, and
percpu_btf_ptr_types.
- Add a missing PTR_TO_BTF_ID | PTR_WALKED switch case entry in
check_func_arg_reg_off(), which is required when validating helper
calls (Kumar)
- Update reg_type_mismatch_ok() to check base types for the registers
(i.e. to accommodate type modifiers). Additionally, add a lengthy
comment that explains why this is being done (Kumar)
- Update convert_ctx_accesses() to also issue probe reads for
PTR_TO_BTF_ID | PTR_WALKED (Kumar)
- Update selftests to expect new prefix reg type strings.
- Rename task_kfunc_acquire_trusted_nested testcase to
task_kfunc_acquire_trusted_walked, and fix a comment (Kumar)
- Remove KF_TRUSTED_ARGS from bpf_task_release(), which already includes
KF_RELEASE (Kumar)
- Add bpf-next in patch subject lines (Kumar)
v4 -> v5:
- Fix an improperly formatted patch title.
v3 -> v4:
- Remove an unnecessary check from my repository that I forgot to remove
after debugging something.
v2 -> v3:
- Make bpf_task_acquire() check for NULL, and include KF_RET_NULL
(Martin)
- Include new PTR_NESTED register modifier type flag which specifies
whether a pointer was obtained from walking a struct. Use this to
expand the meaning of KF_TRUSTED_ARGS to include trusted pointers that
were passed from the kernel (Kumar)
- Add more selftests to the task_kfunc selftest suite which verify that
you cannot pass a walked pointer to bpf_task_acquire().
- Update bpf_task_acquire() to also specify KF_TRUSTED_ARGS.
v1 -> v2:
- Rename tracing_btf_ids to generic_kfunc_btf_ids, and add the new
kfuncs to that list instead of making a separate btf id list (Alexei).
- Don't run the new selftest suite on s390x, which doesn't appear to
support invoking kfuncs.
- Add a missing __diag_ignore block for -Wmissing-prototypes
(lkp@intel.com).
- Fix formatting on some of the SPDX-License-Identifier tags.
- Clarified the function header comment a bit on bpf_task_kptr_get().
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
A previous change added a series of kfuncs for storing struct
task_struct objects as referenced kptrs. This patch adds a new
task_kfunc test suite for validating their expected behavior.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Now that BPF supports adding new kernel functions with kfuncs, and
storing kernel objects in maps with kptrs, we can add a set of kfuncs
which allow struct task_struct objects to be stored in maps as
referenced kptrs. The possible use cases for doing this are plentiful.
During tracing, for example, it would be useful to be able to collect
some tasks that performed a certain operation, and then periodically
summarize who they are, which cgroup they're in, how much CPU time
they've utilized, etc.
In order to enable this, this patch adds three new kfuncs:
struct task_struct *bpf_task_acquire(struct task_struct *p);
struct task_struct *bpf_task_kptr_get(struct task_struct **pp);
void bpf_task_release(struct task_struct *p);
A follow-on patch will add selftests validating these kfuncs.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-4-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Kfuncs currently support specifying the KF_TRUSTED_ARGS flag to signal
to the verifier that it should enforce that a BPF program passes it a
"safe", trusted pointer. Currently, "safe" means that the pointer is
either PTR_TO_CTX, or is refcounted. There may be cases, however, where
the kernel passes a BPF program a safe / trusted pointer to an object
that the BPF program wishes to use as a kptr, but because the object
does not yet have a ref_obj_id from the perspective of the verifier, the
program would be unable to pass it to a KF_ACQUIRE | KF_TRUSTED_ARGS
kfunc.
The solution is to expand the set of pointers that are considered
trusted according to KF_TRUSTED_ARGS, so that programs can invoke kfuncs
with these pointers without getting rejected by the verifier.
There is already a PTR_UNTRUSTED flag that is set in some scenarios,
such as when a BPF program reads a kptr directly from a map
without performing a bpf_kptr_xchg() call. These pointers of course can
and should be rejected by the verifier. Unfortunately, however,
PTR_UNTRUSTED does not cover all the cases for safety that need to
be addressed to adequately protect kfuncs. Specifically, pointers
obtained by a BPF program "walking" a struct are _not_ considered
PTR_UNTRUSTED according to BPF. For example, say that we were to add a
kfunc called bpf_task_acquire(), with KF_ACQUIRE | KF_TRUSTED_ARGS, to
acquire a struct task_struct *. If we only used PTR_UNTRUSTED to signal
that a task was unsafe to pass to a kfunc, the verifier would mistakenly
allow the following unsafe BPF program to be loaded:
SEC("tp_btf/task_newtask")
int BPF_PROG(unsafe_acquire_task,
struct task_struct *task,
u64 clone_flags)
{
struct task_struct *acquired, *nested;
nested = task->last_wakee;
/* Would not be rejected by the verifier. */
acquired = bpf_task_acquire(nested);
if (!acquired)
return 0;
bpf_task_release(acquired);
return 0;
}
To address this, this patch defines a new type flag called PTR_TRUSTED
which tracks whether a PTR_TO_BTF_ID pointer is safe to pass to a
KF_TRUSTED_ARGS kfunc or a BPF helper function. PTR_TRUSTED pointers are
passed directly from the kernel as a tracepoint or struct_ops callback
argument. Any nested pointer that is obtained from walking a PTR_TRUSTED
pointer is no longer PTR_TRUSTED. From the example above, the struct
task_struct *task argument is PTR_TRUSTED, but the 'nested' pointer
obtained from 'task->last_wakee' is not PTR_TRUSTED.
A subsequent patch will add kfuncs for storing a task kfunc as a kptr,
and then another patch will add selftests to validate.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-3-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
