Re: [syzbot] [hardening?] [mm?] BUG: bad usercopy in vfs_readlink

[Jan Kara]

 On Tue 04-02-25 01:46:28, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    69b8923f5003 Merge tag 'for-linus-6.14-ofs4' of git://git...
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1258aeb0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=57ab43c279fa614d
> dashboard link: https://syzkaller.appspot.com/bug?extid=48a99e426f29859818c0
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15825724580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1658aeb0580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ea84ac864e92/disk-69b8923f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6a465997b4e0/vmlinux-69b8923f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/d72b67b2bd15/bzImage-69b8923f.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/7c2919610764/mount_0.gz
> 
> The issue was bisected to:
> 
> commit bae80473f7b0b25772619e7692019b1549d4a82c
> Author: Mateusz Guzik <mjguzik@xxxxxxxxx>
> Date:   Wed Nov 20 11:20:35 2024 +0000
> 
>     ext4: use inode_set_cached_link()
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1248c3df980000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=1148c3df980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1648c3df980000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+48a99e426f29859818c0@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: bae80473f7b0 ("ext4: use inode_set_cached_link()")

Please check attached patch:

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

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR