Re: [PATCH] f2fs: fix to do sanity check correctly on i_inline_xattr_size

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 12/16, Chao Yu wrote:
> syzbot reported an out-of-range access issue as below:
> 
> UBSAN: array-index-out-of-bounds in fs/f2fs/f2fs.h:3292:19
> index 18446744073709550491 is out of range for type '__le32[923]' (aka 'unsigned int[923]')
> CPU: 0 UID: 0 PID: 5338 Comm: syz.0.0 Not tainted 6.12.0-syzkaller-10689-g7af08b57bcb9 #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
>  ubsan_epilogue lib/ubsan.c:231 [inline]
>  __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429
>  read_inline_xattr+0x273/0x280
>  lookup_all_xattrs fs/f2fs/xattr.c:341 [inline]
>  f2fs_getxattr+0x57b/0x13b0 fs/f2fs/xattr.c:533
>  vfs_getxattr_alloc+0x472/0x5c0 fs/xattr.c:393
>  ima_read_xattr+0x38/0x60 security/integrity/ima/ima_appraise.c:229
>  process_measurement+0x117a/0x1fb0 security/integrity/ima/ima_main.c:353
>  ima_file_check+0xd9/0x120 security/integrity/ima/ima_main.c:572
>  security_file_post_open+0xb9/0x280 security/security.c:3121
>  do_open fs/namei.c:3830 [inline]
>  path_openat+0x2ccd/0x3590 fs/namei.c:3987
>  do_file_open_root+0x3a7/0x720 fs/namei.c:4039
>  file_open_root+0x247/0x2a0 fs/open.c:1382
>  do_handle_open+0x85b/0x9d0 fs/fhandle.c:414
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> index: 18446744073709550491 (decimal, unsigned long long)
> = 0xfffffffffffffb9b (hexadecimal) = -1125 (decimal, long long)
> UBSAN detects that inline_xattr_addr() tries to access .i_addr[-1125].
> 
> w/ below testcase, it can reproduce this bug easily:
> - mkfs.f2fs -f -O extra_attr,flexible_inline_xattr /dev/sdb
> - mount -o inline_xattr_size=512 /dev/sdb /mnt/f2fs
> - touch /mnt/f2fs/file
> - umount /mnt/f2fs
> - inject.f2fs --node --mb i_inline --nid 4 --val 0x1 /dev/sdb
> - inject.f2fs --node --mb i_inline_xattr_size --nid 4 --val 2048 /dev/sdb
> - mount /dev/sdb /mnt/f2fs
> - getfattr /mnt/f2fs/file
> 
> The root cause is if metadata of filesystem and inode were fuzzed as below:
> - extra_attr feature is enabled
> - flexible_inline_xattr feature is enabled
> - ri.i_inline_xattr_size = 2048
> - F2FS_EXTRA_ATTR bit in ri.i_inline was not set
> 
> sanity_check_inode() will skip doing sanity check on fi->i_inline_xattr_size,
> result in using invalid inline_xattr_size later incorrectly, fix it.
> 
> Meanwhile, let's fix to check lower boundary for .i_inline_xattr_size w/
> MIN_INLINE_XATTR_SIZE like we did in parse_options().
> 
> Fixes: 6afc662e68b5 ("f2fs: support flexible inline xattr size")
> Reported-by: syzbot+69f5379a1717a0b982a1@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/linux-f2fs-devel/674f4e7d.050a0220.17bd51.004f.GAE@google.com
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
>  fs/f2fs/inode.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> index 282fd320bdb3..29ccc64faae9 100644
> --- a/fs/f2fs/inode.c
> +++ b/fs/f2fs/inode.c
> @@ -302,15 +302,6 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
>  				  F2FS_TOTAL_EXTRA_ATTR_SIZE);
>  			return false;
>  		}
> -		if (f2fs_sb_has_flexible_inline_xattr(sbi) &&
> -			f2fs_has_inline_xattr(inode) &&
> -			(!fi->i_inline_xattr_size ||
> -			fi->i_inline_xattr_size > MAX_INLINE_XATTR_SIZE)) {
> -			f2fs_warn(sbi, "%s: inode (ino=%lx) has corrupted i_inline_xattr_size: %d, max: %lu",
> -				  __func__, inode->i_ino, fi->i_inline_xattr_size,
> -				  MAX_INLINE_XATTR_SIZE);
> -			return false;
> -		}
>  		if (f2fs_sb_has_compression(sbi) &&
>  			fi->i_flags & F2FS_COMPR_FL &&
>  			F2FS_FITS_IN_INODE(ri, fi->i_extra_isize,
> @@ -320,6 +311,16 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
>  		}
>  	}
>  
> +	if (f2fs_sb_has_flexible_inline_xattr(sbi) &&
> +		f2fs_has_inline_xattr(inode) &&
> +		(fi->i_inline_xattr_size < MIN_INLINE_XATTR_SIZE ||
> +		fi->i_inline_xattr_size > MAX_INLINE_XATTR_SIZE)) {
> +		f2fs_warn(sbi, "%s: inode (ino=%lx) has corrupted i_inline_xattr_size: %d, min: %u, max: %lu",
												--> %lu?
> +			  __func__, inode->i_ino, fi->i_inline_xattr_size,
> +			  MIN_INLINE_XATTR_SIZE, MAX_INLINE_XATTR_SIZE);
> +		return false;
> +	}
> +
>  	if (!f2fs_sb_has_extra_attr(sbi)) {
>  		if (f2fs_sb_has_project_quota(sbi)) {
>  			f2fs_warn(sbi, "%s: corrupted inode ino=%lx, wrong feature flag: %u, run fsck to fix.",
> -- 
> 2.40.1