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Kumar Kartikeya Dwivedi cf353904a8 bpf: Detect IP == ksym.end as part of BPF program 
[ Upstream commit 66d9111f35 ]

Now that bpf_throw kfunc is the first such call instruction that has
noreturn semantics within the verifier, this also kicks in dead code
elimination in unprecedented ways. For one, any instruction following
a bpf_throw call will never be marked as seen. Moreover, if a callchain
ends up throwing, any instructions after the call instruction to the
eventually throwing subprog in callers will also never be marked as
seen.

The tempting way to fix this would be to emit extra 'int3' instructions
which bump the jited_len of a program, and ensure that during runtime
when a program throws, we can discover its boundaries even if the call
instruction to bpf_throw (or to subprogs that always throw) is emitted
as the final instruction in the program.

An example of such a program would be this:

do_something():
	...
	r0 = 0
	exit

foo():
	r1 = 0
	call bpf_throw
	r0 = 0
	exit

bar(cond):
	if r1 != 0 goto pc+2
	call do_something
	exit
	call foo
	r0 = 0  // Never seen by verifier
	exit	//

main(ctx):
	r1 = ...
	call bar
	r0 = 0
	exit

Here, if we do end up throwing, the stacktrace would be the following:

bpf_throw
foo
bar
main

In bar, the final instruction emitted will be the call to foo, as such,
the return address will be the subsequent instruction (which the JIT
emits as int3 on x86). This will end up lying outside the jited_len of
the program, thus, when unwinding, we will fail to discover the return
address as belonging to any program and end up in a panic due to the
unreliable stack unwinding of BPF programs that we never expect.

To remedy this case, make bpf_prog_ksym_find treat IP == ksym.end as
part of the BPF program, so that is_bpf_text_address returns true when
such a case occurs, and we are able to unwind reliably when the final
instruction ends up being a call instruction.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230912233214.1518551-12-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-11-28 16:56:15 +00:00
arch x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size 2023-11-28 16:56:15 +00:00
block blk-core: use pr_warn_ratelimited() in bio_check_ro() 2023-11-20 11:08:29 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: lrw,xts - Replace strlcpy with strscpy 2023-09-23 11:09:55 +02:00
Documentation Documentation: sysctl: align cells in second content column 2023-10-25 11:58:54 +02:00
drivers atl1c: Work around the DMA RX overflow issue 2023-11-28 16:56:15 +00:00
fs btrfs: use u64 for buffer sizes in the tree search ioctls 2023-11-20 11:08:30 +01:00
include workqueue: Provide one lock class key per work_on_cpu() callsite 2023-11-28 16:56:15 +00:00
init x86/mm: Initialize text poking earlier 2023-08-08 19:58:33 +02:00
io_uring io_uring/fs: remove sqe->rw_flags checking from LINKAT 2023-10-06 13:18:22 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel bpf: Detect IP == ksym.end as part of BPF program 2023-11-28 16:56:15 +00:00
lib lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default 2023-10-25 11:58:54 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm vfs: fix readahead(2) on block devices 2023-11-20 11:08:13 +01:00
net wifi: mac80211: don't return unset power in ieee80211_get_tx_power() 2023-11-28 16:56:15 +00:00
samples samples/hw_breakpoint: fix building without module unloading 2023-09-23 11:10:01 +02:00
scripts modpost: fix tee MODULE_DEVICE_TABLE built on big-endian host 2023-11-20 11:08:26 +01:00
security KEYS: trusted: Remove redundant static calls usage 2023-10-19 23:05:33 +02:00
sound ASoC: hdmi-codec: register hpd callback on component probe 2023-11-20 11:08:30 +01:00
tools selftests: pmtu.sh: fix result checking 2023-11-20 11:08:29 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:22:40 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-26 14:23:27 +02:00
Makefile Linux 5.15.139 2023-11-20 11:08:30 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.