The following commit has been merged into the perf/urgent branch of tip:
Commit-ID: b583ef82b671c9a752fbe3e95bd4c1c51eab764d
Gitweb: https://git.kernel.org/tip/b583ef82b671c9a752fbe3e95bd4c1c51eab764d
Author: Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Thu, 09 Jan 2025 15:14:40 +01:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 10 Jan 2025 09:28:01 +01:00
uprobes: Fix race in uprobe_free_utask
Max Makarov reported kernel panic [1] in perf user callchain code.
The reason for that is the race between uprobe_free_utask and bpf
profiler code doing the perf user stack unwind and is triggered
within uprobe_free_utask function:
- after current->utask is freed and
- before current->utask is set to NULL
general protection fault, probably for non-canonical address 0x9e759c37ee555c76: 0000 [#1] SMP PTI
RIP: 0010:is_uprobe_at_func_entry+0x28/0x80
...
? die_addr+0x36/0x90
? exc_general_protection+0x217/0x420
? asm_exc_general_protection+0x26/0x30
? is_uprobe_at_func_entry+0x28/0x80
perf_callchain_user+0x20a/0x360
get_perf_callchain+0x147/0x1d0
bpf_get_stackid+0x60/0x90
bpf_prog_9aac297fb833e2f5_do_perf_event+0x434/0x53b
? __smp_call_single_queue+0xad/0x120
bpf_overflow_handler+0x75/0x110
...
asm_sysvec_apic_timer_interrupt+0x1a/0x20
RIP: 0010:__kmem_cache_free+0x1cb/0x350
...
? uprobe_free_utask+0x62/0x80
? acct_collect+0x4c/0x220
uprobe_free_utask+0x62/0x80
mm_release+0x12/0xb0
do_exit+0x26b/0xaa0
__x64_sys_exit+0x1b/0x20
do_syscall_64+0x5a/0x80
It can be easily reproduced by running following commands in
separate terminals:
# while :; do bpftrace -e 'uprobe:/bin/ls:_start { printf("hit\n"); }' -c ls; done
# bpftrace -e 'profile:hz:100000 { @[ustack()] = count(); }'
Fixing this by making sure current->utask pointer is set to NULL
before we start to release the utask object.
[1] https://github.com/grafana/pyroscope/issues/3673
Fixes: cfa7f3d2c526 ("perf,x86: avoid missing caller address in stack traces captured in uprobe")
Reported-by: Max Makarov <maxpain@xxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20250109141440.2692173-1-jolsa@xxxxxxxxxx
---
kernel/events/uprobes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index fa04b14..5d71ef8 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1915,6 +1915,7 @@ void uprobe_free_utask(struct task_struct *t)
if (!utask)
return;
+ t->utask = NULL;
WARN_ON_ONCE(utask->active_uprobe || utask->xol_vaddr);
timer_delete_sync(&utask->ri_timer);
@@ -1924,7 +1925,6 @@ void uprobe_free_utask(struct task_struct *t)
ri = free_ret_instance(ri, true /* cleanup_hprobe */);
kfree(utask);
- t->utask = NULL;
}
#define RI_TIMER_PERIOD (HZ / 10) /* 100 ms */
|