Re: [PATCH] f2fs: reject CASEFOLD inode flag without casefold feature

[Chao Yu]

On 2020/10/9 3:15, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> syzbot reported:
>
>      general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
>      KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
>      CPU: 0 PID: 6860 Comm: syz-executor835 Not tainted 5.9.0-rc8-syzkaller #0
>      Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>      RIP: 0010:utf8_casefold+0x43/0x1b0 fs/unicode/utf8-core.c:107
>      [...]
>      Call Trace:
>       f2fs_init_casefolded_name fs/f2fs/dir.c:85 [inline]
>       __f2fs_setup_filename fs/f2fs/dir.c:118 [inline]
>       f2fs_prepare_lookup+0x3bf/0x640 fs/f2fs/dir.c:163
>       f2fs_lookup+0x10d/0x920 fs/f2fs/namei.c:494
>       __lookup_hash+0x115/0x240 fs/namei.c:1445
>       filename_create+0x14b/0x630 fs/namei.c:3467
>       user_path_create fs/namei.c:3524 [inline]
>       do_mkdirat+0x56/0x310 fs/namei.c:3664
>       do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
>       entry_SYSCALL_64_after_hwframe+0x44/0xa9
>      [...]
>
> The problem is that an inode has F2FS_CASEFOLD_FL set, but the
> filesystem doesn't have the casefold feature flag set, and therefore
> super_block::s_encoding is NULL.
>
> Fix this by making sanity_check_inode() reject inodes that have
> F2FS_CASEFOLD_FL when the filesystem doesn't have the casefold feature.
>
> Reported-by: syzbot+05139c4039d0679e19ff@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups")
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>

Thanks,