syzbot
UBSAN: shift-out-of-bounds in v9fs_mount
Status:
upstream: reported C repro on 2026/07/31 05:29
Reported-by: syzbot+c9a177752bfb0d7dc1c1@syzkaller.appspotmail.com
First crash: 27d, last: 24d
Sample crash report:
syz.0.17[5931]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set
loop0: detected capacity change from 0 to 2048
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
================================================================================
UBSAN: shift-out-of-bounds in fs/9p/vfs_super.c:62:22
shift exponent 32 is too large for 32-bit type 'int'
CPU: 0 PID: 5931 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
ubsan_epilogue+0xa/0x30 lib/ubsan.c:217
__ubsan_handle_shift_out_of_bounds+0x368/0x3f0 lib/ubsan.c:387
v9fs_fill_super fs/9p/vfs_super.c:62 [inline]
v9fs_mount+0xa39/0xb40 fs/9p/vfs_super.c:134
legacy_get_tree+0xea/0x180 fs/fs_context.c:662
vfs_get_tree+0x8c/0x280 fs/super.c:1764
do_new_mount+0x24a/0xa40 fs/namespace.c:3386
do_mount fs/namespace.c:3726 [inline]
__do_sys_mount fs/namespace.c:3935 [inline]
__se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb0e9d9e019
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:00007ffe142714d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fb0ea025fa0 RCX: 00007fb0e9d9e019
RDX: 0000200000002540 RSI: 0000200000002500 RDI: 0000000000000000
RBP: 00007fb0e9e3500c R08: 0000200000000200 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb0ea025fac R14: 00007fb0ea025fa0 R15: 00007fb0ea025fa0
</TASK>
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* Struck through repros no longer work on HEAD.