[syzbot] [io-uring?] WARNING in io_pin_pages (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 83f1454877cc Merge tag 'ext4_for_linus-7.2-rc1' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1211daae580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f1fef3a5f0899512
dashboard link: https://syzkaller.appspot.com/bug?extid=f99b00a963915b6b52c6
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=164b12ae580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=165bb986580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/87171ffb708f/disk-83f14548.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf1d27787991/vmlinux-83f14548.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6e9a56090e11/bzImage-83f14548.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f99b00...@syzkaller.appspotmail.com

------------[ cut here ]------------
!(flags & __GFP_NOWARN)
WARNING: mm/slub.c:6841 at __kvmalloc_node_noprof+0x6f7/0xa60 mm/slub.c:6841, CPU#1: syz.0.17/5823
Modules linked in:
CPU: 1 UID: 0 PID: 5823 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__kvmalloc_node_noprof+0x6f7/0xa60 mm/slub.c:6841
Code: c1 e8 5d 0f ff ff 4d 85 f6 0f 85 21 fd ff ff 48 81 fb ff ff ff 7f 0f 86 b8 fc ff ff 41 81 e4 00 20 00 00 0f 85 07 fd ff ff 90 <0f> 0b 90 e9 fe fc ff ff be 43 01 00 00 48 c7 c7 22 f2 f1 8d e8 a0
RSP: 0018:ffffc9000249fa88 EFLAGS: 00010246
RAX: 0000000000000001 RBX: 0000000080000008 RCX: 0000000100000000
RDX: 0000000000000000 RSI: ffffffff8c1d1100 RDI: ffffffff8e1e6928
RBP: 000000d6000000ca R08: 00000000004028c0 R09: 00000000ffffffff
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: 00000000ffffffff R14: 0000000000000000 R15: 00000000004028c0
FS: 000055556bd29500(0000) GS:ffff88812442d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd3d173e44 CR3: 0000000076c8e000 CR4: 00000000003526f0
Call Trace:
<TASK>
io_pin_pages+0xc3/0x1e0 io_uring/memmap.c:59
io_sqe_buffer_register+0x1d9/0x1500 io_uring/rsrc.c:884
io_sqe_buffers_register.cold+0x346/0x4c3 io_uring/rsrc.c:995
__io_uring_register io_uring/register.c:767 [inline]
__do_sys_io_uring_register+0x13ce/0x1bc0 io_uring/register.c:1029
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcd6539ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc5b4af188 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab
RAX: ffffffffffffffda RBX: 00007fcd65615fa0 RCX: 00007fcd6539ce59
RDX: 0000200000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: 00007fcd65432e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcd65615fac R14: 00007fcd65615fa0 R15: 00007fcd65615fa0
</TASK>


---
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***

Subject: [PATCH] io_uring/memmap: bound io_pin_pages() by page array byte size
Author: karti...@gmail.com

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


io_pin_pages() checks that nr_pages does not exceed INT_MAX, then
allocates a struct page * array of nr_pages entries. kvmalloc() limits
allocations to INT_MAX bytes, but the check counts pages, not bytes.
On 64-bit each entry is 8 bytes, so the array hits the INT_MAX byte
limit at INT_MAX / sizeof(struct page *) pages, well before the page
count check fires.

Since commit d760d3f59f0d ("io_uring/rsrc: raise registered buffer 1GB
limit") raised the per-buffer cap to 1TB, a buffer near that cap maps
~2^28 pages, making the array allocation exceed INT_MAX bytes. This
passes the page count check, reaches kvmalloc(), and triggers the
WARN_ON_ONCE() for oversized allocations in __kvmalloc_node_noprof().

Check nr_pages against INT_MAX / sizeof(struct page *) so the buffer is
rejected with -EOVERFLOW before the allocation is attempted.

Reported-by: syzbot+f99b00...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f99b00a963915b6b52c6
Fixes: b4e41050b212 ("io_uring/rsrc: raise registered buffer 1GB limit")
Signed-off-by: Deepanshu Kartikey <karti...@gmail.com>
---
io_uring/memmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/memmap.c b/io_uring/memmap.c
index 4f9b439319c4..da1f6c5d07f8 100644
--- a/io_uring/memmap.c
+++ b/io_uring/memmap.c
@@ -53,7 +53,7 @@ struct page **io_pin_pages(unsigned long uaddr, unsigned long len, int *npages)
nr_pages = end - start;
if (WARN_ON_ONCE(!nr_pages))
return ERR_PTR(-EINVAL);
- if (WARN_ON_ONCE(nr_pages > INT_MAX))
+ if (nr_pages > INT_MAX / sizeof(struct page *))
return ERR_PTR(-EOVERFLOW);

pages = kvmalloc_objs(struct page *, nr_pages, GFP_KERNEL_ACCOUNT);
--
2.43.0

[syzbot]

Hello,

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

Reported-by: syzbot+f99b00...@syzkaller.appspotmail.com
Tested-by: syzbot+f99b00...@syzkaller.appspotmail.com

Tested on:

commit: 1a3746cc Merge tag 'strncpy-removal-v7.2-rc1' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15455bd2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8c6bf427c5ef3470

dashboard link: https://syzkaller.appspot.com/bug?extid=f99b00a963915b6b52c6
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

patch: https://syzkaller.appspot.com/x/patch.diff?x=17374d56580000

Note: testing is done by a robot and is best-effort only.