diff options
| author | Breno Leitao <leitao@debian.org> | 2026-07-29 07:44:40 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-07-31 10:32:19 +0200 |
| commit | cc679d7a6303e84d769f2afcde1fc51c51f127cd (patch) | |
| tree | cac7d9148b4bc6d251d312ea6589a16d7f9c3c4c /kernel | |
| parent | f5098b6bae761e346ebcd9da7f95622c04733cff (diff) | |
uprobes: Fix NULL pointer dereference in hprobe_expire()
Forking a task that has a pending uretprobe can oops the kernel with a
NULL pointer dereference in the clone() path:
BUG: kernel NULL pointer dereference, address: 0000000000000018
Oops: 0002 [#1] SMP NOPTI
RIP: 0010:hprobe_expire
CR2: 0000000000000018
Call Trace:
uprobe_copy_process
copy_process
kernel_clone
__x64_sys_clone
do_syscall_64
entry_SYSCALL_64_after_hwframe
This was found on real hosts on Meta fleet.
I've got the impression that this is what is happening:
CPU 1 CPU 2 (traced task)
----- -------------------
hit uprobe, prepare_uretprobe():
hprobe LEASED, refcount >= 1
uprobe_unregister()
put_uprobe(): refcount -> 0
fork() -> dup_utask()
hprobe_expire(hprobe, true)
try_get_uprobe() -> NULL
get_uprobe(NULL) <-- Oops
Only take the extra reference when the uprobe is non-NULL; a NULL means
it is gone and is the correct value to return.
Fixes: dd1a7567784e ("uprobes: SRCU-protect uretprobe lifetime (with timeout)")
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260729-uprobe-v1-1-61896b87c867@debian.org
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/events/uprobes.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 4084e926e284..6300b216012c 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -830,7 +830,7 @@ static struct uprobe *hprobe_expire(struct hprobe *hprobe, bool get) if (try_cmpxchg(&hprobe->state, &hstate, uprobe ? HPROBE_STABLE : HPROBE_GONE)) { /* We won the race, we are the ones to unlock SRCU */ __srcu_read_unlock(&uretprobes_srcu, hprobe->srcu_idx); - return get ? get_uprobe(uprobe) : uprobe; + return get && uprobe ? get_uprobe(uprobe) : uprobe; } /* |