linux-kernel - Re: [syzbot] [fs?] UBSAN: shift-out-of-bounds in befs_check

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Message-ID: <68d9921e.a70a0220.10c4b.0025.GAE@google.com>
Date: Sun, 28 Sep 2025 12:53:02 -0700
From: syzbot <syzbot+fc26c366038b54261e53@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	xandfury@...il.com
Subject: Re: [syzbot] [fs?] UBSAN: shift-out-of-bounds in befs_check_sb

Hello,

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

./include/linux/thread_info.h:244:4: error: call to '__bad_copy_from' declared with 'error' attribute: copy source size is too small
drivers/nvme/target/fc.c:150:2: warning: 'counted_by' should not be applied to an array with element of unknown size because 'struct nvmet_fc_fcp_iod' is a struct type with a flexible array member. This will be an error in a future compiler version [-Wbounds-safety-counted-by-elt-type-unknown-size]

Tested on:

commit:         6f861765 fs: Block writes to mounted block devices
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel config:  https://syzkaller.appspot.com/x/.config?x=f5b21423ca3f0a96
dashboard link: https://syzkaller.appspot.com/bug?extid=fc26c366038b54261e53
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.