[v5.15] KASAN: stack-out-of-bounds Read in gfs2_file_read_iter (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 241d66fa280c Linux 5.15.208
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=139f7ed2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=09675e90f1ef60d6ed3d
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d3e9d10633a1/disk-241d66fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/beca1f713e4b/vmlinux-241d66fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/26a15a6e1c14/bzImage-241d66fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+09675e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: stack-out-of-bounds in should_fault_in_pages fs/gfs2/file.c:785 [inline]
BUG: KASAN: stack-out-of-bounds in gfs2_file_read_iter+0x8e1/0xda0 fs/gfs2/file.c:995
Read of size 8 at addr ffffc90003327d50 by task syz.2.736/7384

CPU: 1 PID: 7384 Comm: syz.2.736 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
should_fault_in_pages fs/gfs2/file.c:785 [inline]
gfs2_file_read_iter+0x8e1/0xda0 fs/gfs2/file.c:995
call_read_iter include/linux/fs.h:2167 [inline]
new_sync_read fs/read_write.c:404 [inline]
vfs_read+0x759/0xd60 fs/read_write.c:485
ksys_read+0x152/0x260 fs/read_write.c:623
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f76e2874e59
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:00007f76e0aad028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f76e2aee090 RCX: 00007f76e2874e59
RDX: 0000000000002020 RSI: 0000200000001300 RDI: 0000000000000004
RBP: 00007f76e290ad6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f76e2aee128 R14: 00007f76e2aee090 R15: 00007ffe70853108
</TASK>


addr ffffc90003327d50 is located in stack of task syz.2.736/7384 at offset 48 in frame:
vfs_read+0x0/0xd60

this frame has 3 objects:
[32, 48) 'iov.i'
[64, 112) 'kiocb.i'
[144, 184) 'iter.i'

Memory state around the buggy address:
ffffc90003327c00: 00 00 00 00 00 00 00 f3 f3 f3 f3 f3 00 00 00 00
ffffc90003327c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90003327d00: 00 00 00 00 f1 f1 f1 f1 00 00 f2 f2 00 00 00 00
^
ffffc90003327d80: 00 00 f2 f2 f2 f2 00 00 00 00 00 f3 f3 f3 f3 f3
ffffc90003327e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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