From: Breno Leitao Date: Wed, 29 Jul 2026 14:44:40 +0000 (-0700) Subject: uprobes: Fix NULL pointer dereference in hprobe_expire() X-Git-Tag: v7.2-rc6~5^2 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=cc679d7a6303e84d769f2afcde1fc51c51f127cd;p=thirdparty%2Flinux.git 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 Signed-off-by: Peter Zijlstra (Intel) Acked-by: Oleg Nesterov Acked-by: Andrii Nakryiko Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260729-uprobe-v1-1-61896b87c867@debian.org --- 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; } /*