memory leak in io_submit_sqes

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d6efb3ac Merge tag 'tty-5.9-rc1' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13cb0762900000
kernel config: https://syzkaller.appspot.com/x/.config?x=42163327839348a9
dashboard link: https://syzkaller.appspot.com/bug?extid=a730016dc0bdce4f6ff5
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16e877dc900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1608291a900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a73001...@syzkaller.appspotmail.com

executing program
executing program
executing program
executing program
executing program
BUG: memory leak
unreferenced object 0xffff888124949100 (size 256):
comm "syz-executor808", pid 6480, jiffies 4294949911 (age 33.960s)
hex dump (first 32 bytes):
00 78 74 2a 81 88 ff ff 00 00 00 00 00 00 00 00 .xt*............
90 b0 51 81 ff ff ff ff 00 00 00 00 00 00 00 00 ..Q.............
backtrace:
[<0000000084e46f34>] io_alloc_req fs/io_uring.c:1503 [inline]
[<0000000084e46f34>] io_submit_sqes+0x5dc/0xc00 fs/io_uring.c:6306
[<000000006d4e19eb>] __do_sys_io_uring_enter+0x582/0x830 fs/io_uring.c:8036
[<00000000a4116b07>] do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
[<0000000067b2aefc>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff88811751d200 (size 96):
comm "syz-executor808", pid 6480, jiffies 4294949911 (age 33.960s)
hex dump (first 32 bytes):
00 78 74 2a 81 88 ff ff 00 00 00 00 00 00 00 00 .xt*............
0e 01 00 00 00 00 75 22 00 00 00 00 00 0f 1f 04 ......u"........
backtrace:
[<00000000073ea2ba>] kmalloc include/linux/slab.h:555 [inline]
[<00000000073ea2ba>] io_arm_poll_handler fs/io_uring.c:4773 [inline]
[<00000000073ea2ba>] __io_queue_sqe+0x445/0x6b0 fs/io_uring.c:5988
[<000000001551bde0>] io_queue_sqe+0x309/0x550 fs/io_uring.c:6060
[<000000002dfb908f>] io_submit_sqe fs/io_uring.c:6130 [inline]
[<000000002dfb908f>] io_submit_sqes+0x8b8/0xc00 fs/io_uring.c:6327
[<000000006d4e19eb>] __do_sys_io_uring_enter+0x582/0x830 fs/io_uring.c:8036
[<00000000a4116b07>] do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
[<0000000067b2aefc>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



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[Jens Axboe]

This one looks very odd, and I cannot reproduce it. The socket() calls
reliably fails for me, and even if I hack it to use 0 for protocol instead
of 2, I don't see anything interesting happening here. An IORING_OP_WRITEV
is submitted on the socket, which just fails with ENOTCONN.

--
Jens Axboe

[Jens Axboe]

Dug a bit deeper and found the missing option, I can now reproduce this!
I'll take a look.

--
Jens Axboe

[Jens Axboe]

This should fix it.

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 99582cf5106b..8a2afd8c33c9 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4883,7 +4883,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req)

ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask,
io_async_wake);
- if (ret) {
+ if (ret || ipt.error) {
io_poll_remove_double(req, apoll->double_poll);
spin_unlock_irq(&ctx->completion_lock);
kfree(apoll->double_poll);

--
Jens Axboe