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linux/include/trace/events
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Kalesh Singh 5ca9a617fc mm/tracing: rss_stat: ensure curr is false from kthread context 
commit 079c24d569 upstream.

The rss_stat trace event allows userspace tools, like Perfetto [1], to
inspect per-process RSS metric changes over time.

The curr field was introduced to rss_stat in commit e4dcad204d
("rss_stat: add support to detect RSS updates of external mm").  Its
intent is to indicate whether the RSS update is for the mm_struct of the
current execution context; and is set to false when operating on a remote
mm_struct (e.g., via kswapd or a direct reclaimer).

However, an issue arises when a kernel thread temporarily adopts a user
process's mm_struct.  Kernel threads do not have their own mm_struct and
normally have current->mm set to NULL.  To operate on user memory, they
can "borrow" a memory context using kthread_use_mm(), which sets
current->mm to the user process's mm.

This can be observed, for example, in the USB Function Filesystem (FFS)
driver.  The ffs_user_copy_worker() handles AIO completions and uses
kthread_use_mm() to copy data to a user-space buffer.  If a page fault
occurs during this copy, the fault handler executes in the kthread's
context.

At this point, current is the kthread, but current->mm points to the user
process's mm.  Since the rss_stat event (from the page fault) is for that
same mm, the condition current->mm == mm becomes true, causing curr to be
incorrectly set to true when the trace event is emitted.

This is misleading because it suggests the mm belongs to the kthread,
confusing userspace tools that track per-process RSS changes and
corrupting their mm_id-to-process association.

Fix this by ensuring curr is always false when the trace event is emitted
from a kthread context by checking for the PF_KTHREAD flag.

Link: https://lkml.kernel.org/r/20260219233708.1971199-1-kaleshsingh@google.com
Link: https://perfetto.dev/ [1]
Fixes: e4dcad204d ("rss_stat: add support to detect RSS updates of external mm")
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>	[5.10+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-04-18 10:33:14 +02:00
..
9p.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
afs.h afs: Use refcount_t rather than atomic_t 2024-01-05 15:13:30 +01:00
alarmtimer.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
asoc.h ASoC: tracing: Export SND_SOC_DAPM_DIR_OUT to its value 2024-06-16 13:39:29 +02:00
avc.h selinux: add basic filtering for audit trace events 2020-08-21 17:07:29 -04:00
bcache.h block: remove superfluous param in blk_fill_rwbs() 2021-02-22 06:37:41 -07:00
block.h blktrace: fix blk_rq_merge documentation 2021-02-22 06:37:41 -07:00
bpf_test_run.h selftests: bpf: test writable buffers in raw tps 2019-04-26 19:04:19 -07:00
bridge.h net: bridge: fdb: br_fdb_update can take flags directly 2019-11-01 10:32:43 -07:00
btrfs.h btrfs: correct the order of prelim_ref arguments in btrfs__prelim_ref 2025-06-04 14:38:05 +02:00
cachefiles.h cachefiles: Fix oops with cachefiles_cull() due to NULL object 2021-10-05 11:22:06 +01:00
cgroup.h cgroup: Trace event cgroup id fields should be u64 2022-01-27 11:03:23 +01:00
clk.h clk: Trace clk_set_rate() "range" functions 2020-12-17 01:54:31 -08:00
cma.h mm, tracing: unify PFN format strings 2021-06-29 10:53:52 -07:00
compaction.h mm/page_alloc: integrate classzone_idx and high_zoneidx 2020-06-03 20:09:44 -07:00
context_tracking.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cpuhp.h treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively 2019-04-09 14:19:06 +02:00
damon.h mm/damon: add a tracepoint 2021-09-08 11:50:24 -07:00
devfreq.h PM / devfreq: Add tracepoint for frequency changes 2020-10-26 10:52:37 +09:00
devlink.h devlink: Add a tracepoint for trap reports 2020-09-30 18:01:26 -07:00
dma_fence.h treewide: Add missing semicolons to __assign_str uses 2021-06-30 09:19:14 -04:00
erofs.h erofs: remove unused trace event erofs_destroy_inode 2025-06-27 11:05:35 +01:00
error_report.h tracing: add error_report_end trace point 2021-02-26 09:41:02 -08:00
ext4.h ext4: disable fast-commit of encrypted dir operations 2023-01-12 11:59:04 +01:00
f2fs.h f2fs: reduce expensive checkpoint trigger frequency 2024-10-17 15:11:04 +02:00
fib.h net: Replace nhc_has_gw with nhc_gw_family 2019-04-08 15:22:40 -07:00
fib6.h ipv6: Add fib6_type and fib6_flags to fib6_result 2019-04-17 23:11:30 -07:00
filelock.h filelock: add FL_RECLAIM to show_fl_flags() macro 2025-10-19 16:21:28 +02:00
filemap.h mm, tracing: unify PFN format strings 2021-06-29 10:53:52 -07:00
fs_dax.h libnvdimm for 4.15 2017-11-17 09:51:57 -08:00
fscache.h fscache: Use refcount_t for the cookie refcount instead of atomic_t 2021-08-27 13:34:03 +01:00
fsi.h trace: fsi: Print transfer size unsigned 2019-11-08 11:23:37 +01:00
fsi_master_aspeed.h fsi: aspeed: Add trace points 2019-11-08 11:28:20 +01:00
fsi_master_ast_cf.h fsi: master-ast-cf: Add new FSI master using Aspeed ColdFire 2018-07-23 15:22:52 +10:00
fsi_master_gpio.h fsi: master-gpio: Add more tracepoints 2018-07-12 12:02:31 +10:00
gpio.h tracing: stop making gpio tracing configurable 2019-04-08 15:11:48 +02:00
gpu_mem.h gpu/trace: Minor comment updates for gpu_mem_total tracepoint 2020-05-07 13:32:57 -04:00
host1x.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
huge_memory.h khugepaged: introduce 'max_ptes_shared' tunable 2020-06-03 20:09:46 -07:00
hwmon.h hwmon: (core) Add trace events to _attr_show/store functions 2018-10-11 20:07:35 -07:00
i2c.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
ib_mad.h IB/mad: Don't call to function that might sleep while in atomic context 2022-12-31 13:14:23 +01:00
ib_umad.h IB/UMAD: Add umad trace points 2019-03-27 15:52:01 -03:00
initcall.h tracing: initcall: Ordered comparison of function pointers 2018-04-26 15:02:46 -04:00
intel-sst.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
intel_iommu.h iommu/vt-d: Add prq_report trace event 2021-06-10 09:06:13 +02:00
intel_ish.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
io_uring.h io_uring: io_uring_complete() trace should take an integer 2021-09-03 16:59:06 -06:00
iocost.h blk-iocost: Add iocg idle state tracepoint 2020-12-17 07:55:44 -07:00
iommu.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ipi.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
irq.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
irq_matrix.h genirq/matrix: Add tracepoints 2017-09-25 20:38:26 +02:00
iscsi.h scsi: iscsi: Capture iscsi debug messages using tracepoints 2018-12-20 20:03:55 -05:00
jbd2.h jbd2: remove journal_clean_one_cp_list() 2023-08-30 16:18:12 +02:00
kmem.h mm/tracing: rss_stat: ensure curr is false from kthread context 2026-04-18 10:33:14 +02:00
kvm.h KVM: x86/mmu: Drop trace_kvm_age_page() tracepoint 2021-04-17 08:30:56 -04:00
kyber.h kyber: avoid q->disk dereferences in trace points 2021-10-15 21:02:57 -06:00
libata.h ata: libata: add qc->flags in ata_qc_complete_template tracepoint 2022-06-29 09:03:20 +02:00
lock.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mce.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mdio.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
migrate.h mm/migrate: demote pages during reclaim 2021-09-03 09:58:16 -07:00
mlxsw.h mlxsw: spectrum_acl: Rename rehash_dis trace 2019-03-31 11:01:23 -07:00
mmap.h mm: mmap: add trace point of vm_unmapped_area 2020-04-02 09:35:30 -07:00
mmap_lock.h mm: mmap_lock: add tracepoints around lock acquisition 2020-12-15 12:13:41 -08:00
mmc.h mmc: core: Fix tracepoint print of blk_addr and blksz 2018-03-15 11:15:22 +01:00
mmflags.h Merge branch 'akpm' (patches from Andrew) 2021-09-08 12:55:35 -07:00
module.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mptcp.h mptcp: sched: check both directions for backup 2024-08-19 05:45:47 +02:00
napi.h tracing: Fix header include guards in trace event headers 2019-07-30 21:49:06 -04:00
nbd.h nbd: add tracepoints for send/receive timing 2019-04-26 19:04:19 -07:00
neigh.h neighbor: tracing: Move pin6 inside CONFIG_IPV6=y section 2023-10-25 11:58:57 +02:00
net.h net: use %px to print skb address in trace_netif_receive_skb 2021-07-15 10:28:48 -07:00
net_probe_common.h net: dccp: Add DCCP sendmsg trace event 2018-01-02 14:27:30 -05:00
netfs.h netfs: Move cookie debug ID to struct netfs_cache_resources 2021-08-25 15:20:25 +01:00
netlink.h netlink: add tracepoint at NL_SET_ERR_MSG 2021-02-04 18:05:59 -08:00
nilfs2.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nmi.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
objagg.h lib: introduce initial implementation of object aggregation manager 2018-11-15 14:43:43 -08:00
oom.h mm: update mark_victim tracepoints fields 2025-03-13 12:50:48 +01:00
osnoise.h tracing: Fix spelling in osnoise tracer "interferences" -> "interference" 2021-06-28 14:12:27 -04:00
page_isolation.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
page_pool.h mm, tracing: unify PFN format strings 2021-06-29 10:53:52 -07:00
page_ref.h mm: introduce PAGEFLAGS_MASK to replace ((1UL << NR_PAGEFLAGS) - 1) 2021-09-08 11:50:24 -07:00
pagemap.h mm, tracing: unify PFN format strings 2021-06-29 10:53:52 -07:00
percpu.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
power.h PM: QoS: Simplify definitions of CPU latency QoS trace events 2020-02-13 11:26:39 +01:00
power_cpu_migrate.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
preemptirq.h tracing: Change offset type to s32 in preempt/irq tracepoints 2020-01-03 11:34:37 -05:00
printk.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pwc.h media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler() 2019-01-16 11:15:11 -05:00
pwm.h pwm: Implement tracing for .get_state() and .apply_state() 2020-01-20 12:28:37 +01:00
qdisc.h tracing/net_sched: NULL pointer dereference in perf_trace_qdisc_reset() 2024-07-05 09:14:52 +02:00
qla.h scsi: qla2xxx: Suppress two recently introduced compiler warnings 2020-05-19 21:43:01 -04:00
qrtr.h net: qrtr: correct types of trace event parameters 2023-05-11 23:00:27 +09:00
rcu.h rcu: Fix rcu_torture_read ftrace event 2023-04-05 11:25:00 +02:00
rdma_core.h RDMA/core: Add trace points to follow MR allocation 2020-01-07 16:10:53 -04:00
regulator.h regulator: core: Add regulator bypass trace points 2020-05-29 17:17:02 +01:00
rpcgss.h SUNRPC: Fixup gss_status tracepoint error output 2024-08-19 05:45:04 +02:00
rpcrdma.h trace: Relocate event helper files 2024-04-10 16:19:24 +02:00
rpm.h PM-runtime: add tracepoints for usage_count changes 2020-01-13 12:28:29 +01:00
rseq.h rseq: Introduce restartable sequences system call 2018-06-06 11:58:31 +02:00
rtc.h rtc: Add tracepoints for RTC system 2018-02-13 21:30:22 +01:00
rxrpc.h rxrpc: Use refcount_t rather than atomic_t 2022-12-02 17:41:04 +01:00
sched.h sched/tracing: Remove the redundant 'success' in the sched tracepoint 2021-06-10 11:16:20 -04:00
scmi.h firmware: arm_scmi: Use signed integer to report transfer status 2020-06-30 14:07:08 +01:00
scsi.h scsi: core: Kill message byte 2021-05-31 22:48:24 -04:00
sctp.h sctp: move trace_sctp_probe_path into sctp_outq_sack 2019-12-26 13:06:45 -08:00
signal.h signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
siox.h siox: add support for tracing 2017-12-19 10:56:24 +01:00
skb.h net: ipv4: use kfree_skb_reason() in ip_rcv_finish_core() 2022-07-29 17:25:16 +02:00
smbus.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
sock.h net: sock: tracing: Fix sock_exceed_buf_limit not to dereference stale pointer 2022-07-21 21:24:12 +02:00
spi.h spi: Enable tracing of the SPI setup CS selection 2021-05-26 21:22:13 +01:00
spmi.h spmi: trace: fix stack-out-of-bound access in SPMI tracing functions 2022-08-17 14:24:19 +02:00
sunrpc.h trace: Relocate event helper files 2024-04-10 16:19:24 +02:00
sunvnet.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
swiotlb.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
syscalls.h syscalls: Remove start and number from syscall_get_arguments() args 2019-04-05 09:26:43 -04:00
target.h scsi: target: core: Add CONTROL field for trace events 2020-10-02 18:36:19 -04:00
task.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
tcp.h tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tegra_apb_dma.h tracing: Fix header include guards in trace event headers 2019-07-30 21:49:06 -04:00
thermal.h thermal: devfreq_cooling: change tracing function and arguments 2020-12-11 14:10:44 +01:00
thermal_power_allocator.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
thp.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
timer.h tracing/timer: Add missing hrtimer modes to decode_hrtimer_mode(). 2023-07-23 13:46:45 +02:00
tlb.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
udp.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ufs.h scsi: ufs: core: Enable power management for wlun 2021-05-10 22:28:20 -04:00
v4l2.h media: v4l2: abstract timeval handling in v4l2_buffer 2020-01-03 15:43:35 +01:00
vb2.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
vmscan.h tracing: incorrect isolate_mote_t cast in mm_vmscan_lru_isolate 2022-06-09 10:22:43 +02:00
vsock_virtio_transport_common.h virtio/vsock: update trace event for SEQPACKET 2021-06-11 13:32:47 -07:00
wbt.h bdi: use bdi_dev_name() to get device name 2020-05-09 16:07:39 -06:00
workqueue.h workqueue/tracing: Copy workqueue name to buffer in trace event 2021-03-18 12:57:37 -04:00
writeback.h writeback: fix dereferencing NULL mapping->host on writeback_page_template 2023-06-28 10:29:44 +02:00
xdp.h xdp: Extend xdp_redirect_map with broadcast support 2021-05-26 09:46:16 +02:00
xen.h x86/mm/tlb: Flush remote and local TLBs concurrently 2021-03-06 12:59:10 +01:00