Re: [syzbot] [fs?] KASAN: null-ptr-deref Read in ida_free (3)

[Christian Brauner]

On Wed, Mar 29, 2023 at 05:28:55PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    da8e7da11e4b Merge tag 'nfsd-6.3-4' of git://git.kernel.or..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1266331ec80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=acdb62bf488a8fe5
> dashboard link: https://syzkaller.appspot.com/bug?extid=8ac3859139c685c4f597
> compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11639815c80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12128b1ec80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/62e9c5f4bead/disk-da8e7da1.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/c11aa933e2a7/vmlinux-da8e7da1.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/7a21bdd49c84/bzImage-da8e7da1.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8ac3859139c685c4f597@xxxxxxxxxxxxxxxxxxxxxxxxx

This bug deserves a #include <asm-generic/bitops/ffs.h>.

In any case, it might just be advisable to hold namespace_lock() while
cleaning up peer group ids...

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping.git b4/vfs-mount_setattr-propagation-fix