[syzbot] [io-uring?] [block?] memory leak in io_submit_sqes (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 06cf61899d64 Merge tag 'x86-urgent-2026-08-08' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=118c1132580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6843f8fd2336602d
dashboard link: https://syzkaller.appspot.com/bug?extid=a4ccdd7ebf452e4d4701
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=128c5fb9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15b37fb9580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e023ff6ad9bc/disk-06cf6189.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea49527ba5df/vmlinux-06cf6189.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e3d6468d0490/bzImage-06cf6189.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a4ccdd...@syzkaller.appspotmail.com

BUG: memory leak
unreferenced object 0xffff888112726000 (size 248):
comm "syz.0.17", pid 5956, jiffies 4294942148
hex dump (first 32 bytes):
80 5d 3a 0e 81 88 ff ff d0 03 59 15 81 88 ff ff .]:.......Y.....
04 75 20 c0 02 00 00 80 00 00 00 00 00 00 00 00 .u .............
backtrace (crc e2966ca0):
kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
slab_post_alloc_hook mm/slub.c:4597 [inline]
kmem_cache_alloc_bulk_noprof+0x272/0x3f0 mm/slub.c:7435
__io_alloc_req_refill+0x4a/0x150 io_uring/io_uring.c:988
io_alloc_req io_uring/io_uring.h:536 [inline]
io_submit_sqes.cold+0x16e/0x20b io_uring/io_uring.c:2046
__do_sys_io_uring_enter+0x56d/0xd60 io_uring/io_uring.c:2646
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf8/0x610 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff8881155903c0 (size 192):
comm "syz.0.17", pid 5956, jiffies 4294942148
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
2e 20 00 00 03 00 00 00 04 75 20 c0 00 00 00 00 . .......u .....
backtrace (crc db88fe21):
kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
slab_post_alloc_hook mm/slub.c:4597 [inline]
slab_alloc_node mm/slub.c:4917 [inline]
__do_kmalloc_node mm/slub.c:5333 [inline]
__kmalloc_noprof+0x3bf/0x550 mm/slub.c:5359
_kmalloc_noprof include/linux/slab.h:992 [inline]
io_cache_alloc_new+0x20/0x80 io_uring/alloc_cache.c:40
io_cache_alloc io_uring/alloc_cache.h:61 [inline]
io_uring_alloc_async_data io_uring/io_uring.h:355 [inline]
io_uring_cmd_prep+0x157/0x1f0 io_uring/uring_cmd.c:208
io_init_req io_uring/io_uring.c:1842 [inline]
io_submit_sqe io_uring/io_uring.c:1889 [inline]
io_submit_sqes+0x446/0xd00 io_uring/io_uring.c:2057
__do_sys_io_uring_enter+0x56d/0xd60 io_uring/io_uring.c:2646
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf8/0x610 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff888112726100 (size 248):
comm "syz.0.18", pid 5972, jiffies 4294942449
hex dump (first 32 bytes):
80 d7 55 02 81 88 ff ff d0 a0 50 15 81 88 ff ff ..U.......P.....
04 75 20 c0 02 00 00 80 00 00 00 00 00 00 00 00 .u .............
backtrace (crc dcaddc4c):
kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
slab_post_alloc_hook mm/slub.c:4597 [inline]
kmem_cache_alloc_bulk_noprof+0x272/0x3f0 mm/slub.c:7435
__io_alloc_req_refill+0x4a/0x150 io_uring/io_uring.c:988
io_alloc_req io_uring/io_uring.h:536 [inline]
io_submit_sqes.cold+0x16e/0x20b io_uring/io_uring.c:2046
__do_sys_io_uring_enter+0x56d/0xd60 io_uring/io_uring.c:2646
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xf8/0x610 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

connection error: failed to recv *flatrpc.ExecutorMessageRawT: EOF


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***

Subject: io_uring/cmd: don't skip completion for a non-armed multishot uring_cmd
Author: vasilis...@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git dad19b6f6336e1587b0f767d5b4e2b5543224b43

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index c14c22cff49e..a2899a852879 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -269,7 +269,8 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
}

ret = file->f_op->uring_cmd(ioucmd, issue_flags);
- if (ioucmd->flags & IORING_URING_CMD_MULTISHOT) {
+ if ((ioucmd->flags & IORING_URING_CMD_MULTISHOT) &&
+ (req->flags & REQ_F_APOLL_MULTISHOT)) {
if (ret >= 0)
return IOU_ISSUE_SKIP_COMPLETE;
}

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to checkout kernel repo git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git on commit dad19b6f6336e1587b0f767d5b4e2b5543224b43: failed to run ["git" "-c" "core.hooksPath=/dev/null" "fetch" "--force" "--tags" "f569e972c8e9057ee9c286220c83a480ebf30cc5" "dad19b6f6336e1587b0f767d5b4e2b5543224b43"]: exit status 128


Tested on:

commit: [unknown
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git dad19b6f6336e1587b0f767d5b4e2b5543224b43

kernel config: https://syzkaller.appspot.com/x/.config?x=6843f8fd2336602d
dashboard link: https://syzkaller.appspot.com/bug?extid=a4ccdd7ebf452e4d4701
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=1510a879580000

[Vasileios Almpanis]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 06cf61899d6498b33e4b7c87d99d5bd471ccc375