[PATCH 5.17 0267/1126] watch_queue: Actually free the watch

Greg Kroah-Hartman
2022-04-05T08:04:47Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit 3d8dcf278b1ee1eff1e90be848fa2237db4c07a7 ]

free_watch() does everything barring actually freeing the watch object. Fix
this by adding the missing kfree.

kmemleak produces a report something like the following. Note that as an
address can be seen in the first word, the watch would appear to have gone
through call_rcu().

BUG: memory leak
unreferenced object 0xffff88810ce4a200 (size 96):
comm "syz-executor352", pid 3605, jiffies 4294947473 (age 13.720s)
hex dump (first 32 bytes):
e0 82 48 0d 81 88 ff ff 00 00 00 00 00 00 00 00 ..H.............
80 a2 e4 0c 81 88 ff ff 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff8214e6cc>] kmalloc include/linux/slab.h:581 [inline]
[<ffffffff8214e6cc>] kzalloc include/linux/slab.h:714 [inline]
[<ffffffff8214e6cc>] keyctl_watch_key+0xec/0x2e0 security/keys/keyctl.c:1800
[<ffffffff8214ec84>] __do_sys_keyctl+0x3c4/0x490 security/keys/keyctl.c:2016
[<ffffffff84493a25>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff84493a25>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
[<ffffffff84600068>] entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-and-tested-by: syzbot+6e2de48f06cdb2884bfc@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/watch_queue.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index 5848d4795816..3990e4df3d7b 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -395,6 +395,7 @@ static void free_watch(struct rcu_head *rcu)
put_watch_queue(rcu_access_pointer(watch->queue));
atomic_dec(&watch->cred->user->nr_watches);
put_cred(watch->cred);
+ kfree(watch);
}

static void __put_watch(struct kref *kref)
--
2.34.1