[syzbot] memory leak in iovec_from_user

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ce522ba9ef7e Linux 5.18-rc2
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14225724f00000
kernel config: https://syzkaller.appspot.com/x/.config?x=b8f1a3425e05af27
dashboard link: https://syzkaller.appspot.com/bug?extid=96b43810dfe9c3bb95ed
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13c45d88f00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17b428af700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+96b438...@syzkaller.appspotmail.com

executing program
BUG: memory leak
unreferenced object 0xffff88810d698300 (size 192):
comm "syz-executor156", pid 3595, jiffies 4294944234 (age 12.580s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff823357be>] kmalloc_array include/linux/slab.h:621 [inline]
[<ffffffff823357be>] iovec_from_user lib/iov_iter.c:1922 [inline]
[<ffffffff823357be>] iovec_from_user+0x13e/0x280 lib/iov_iter.c:1905
[<ffffffff82335945>] __import_iovec+0x45/0x250 lib/iov_iter.c:1948
[<ffffffff81668c8e>] __io_import_iovec+0xfe/0x800 fs/io_uring.c:3497
[<ffffffff8166d92f>] io_import_iovec fs/io_uring.c:3508 [inline]
[<ffffffff8166d92f>] io_read+0x59f/0x880 fs/io_uring.c:3803
[<ffffffff816727b4>] io_issue_sqe+0x364/0x3270 fs/io_uring.c:7122
[<ffffffff816761c3>] __io_queue_sqe fs/io_uring.c:7489 [inline]
[<ffffffff816761c3>] io_queue_sqe fs/io_uring.c:7531 [inline]
[<ffffffff816761c3>] io_submit_sqe fs/io_uring.c:7736 [inline]
[<ffffffff816761c3>] io_submit_sqes+0x553/0x3030 fs/io_uring.c:7842
[<ffffffff81679390>] __do_sys_io_uring_enter+0x6f0/0x1100 fs/io_uring.c:10780
[<ffffffff8451ca25>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff8451ca25>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
[<ffffffff84600068>] entry_SYSCALL_64_after_hwframe+0x44/0xae

BUG: memory leak
unreferenced object 0xffff88810d6983c0 (size 192):
comm "syz-executor156", pid 3603, jiffies 4294944759 (age 7.330s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff823357be>] kmalloc_array include/linux/slab.h:621 [inline]
[<ffffffff823357be>] iovec_from_user lib/iov_iter.c:1922 [inline]
[<ffffffff823357be>] iovec_from_user+0x13e/0x280 lib/iov_iter.c:1905
[<ffffffff82335945>] __import_iovec+0x45/0x250 lib/iov_iter.c:1948
[<ffffffff81668c8e>] __io_import_iovec+0xfe/0x800 fs/io_uring.c:3497
[<ffffffff8166d92f>] io_import_iovec fs/io_uring.c:3508 [inline]
[<ffffffff8166d92f>] io_read+0x59f/0x880 fs/io_uring.c:3803
[<ffffffff816727b4>] io_issue_sqe+0x364/0x3270 fs/io_uring.c:7122
[<ffffffff816761c3>] __io_queue_sqe fs/io_uring.c:7489 [inline]
[<ffffffff816761c3>] io_queue_sqe fs/io_uring.c:7531 [inline]
[<ffffffff816761c3>] io_submit_sqe fs/io_uring.c:7736 [inline]
[<ffffffff816761c3>] io_submit_sqes+0x553/0x3030 fs/io_uring.c:7842
[<ffffffff81679390>] __do_sys_io_uring_enter+0x6f0/0x1100 fs/io_uring.c:10780
[<ffffffff8451ca25>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff8451ca25>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
[<ffffffff84600068>] entry_SYSCALL_64_after_hwframe+0x44/0xae



---
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syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Jens Axboe]

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 659f8ecba5b7..d4feb5ca63ba 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3825,8 +3825,10 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
iovec = NULL;
}
ret = io_rw_init_file(req, FMODE_READ);
- if (unlikely(ret))
+ if (unlikely(ret)) {
+ kfree(iovec);
return ret;
+ }
req->result = iov_iter_count(&s->iter);

if (force_nonblock) {
@@ -3951,8 +3953,10 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
iovec = NULL;
}
ret = io_rw_init_file(req, FMODE_WRITE);
- if (unlikely(ret))
+ if (unlikely(ret)) {
+ kfree(iovec);
return ret;
+ }
req->result = iov_iter_count(&s->iter);

if (force_nonblock) {

--
Jens Axboe

[Jens Axboe]

#syz test: git://git.kernel.dk/linux-block io_uring-5.18

--
Jens Axboe

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+96b438...@syzkaller.appspotmail.com

Tested on:

commit: c0713540 io_uring: fix leaks on IOPOLL and CQE_SKIP
git tree: git://git.kernel.dk/linux-block io_uring-5.18

kernel config: https://syzkaller.appspot.com/x/.config?x=b8f1a3425e05af27
dashboard link: https://syzkaller.appspot.com/bug?extid=96b43810dfe9c3bb95ed
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.