linux-kernel - Re: [PATCH] f2fs: fix to do sanity check correctly on i_inline_xattr

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Message-ID: <f282ccdd-2dad-4128-b27a-dd6038622aec@kernel.org>
Date: Fri, 10 Jan 2025 11:23:37 +0800
From: Chao Yu <chao@...nel.org>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: chao@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
 linux-kernel@...r.kernel.org,
 syzbot+69f5379a1717a0b982a1@...kaller.appspotmail.com
Subject: Re: [PATCH] f2fs: fix to do sanity check correctly on
 i_inline_xattr_size

On 1/8/25 03:28, Jaegeuk Kim wrote:
> 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@...kaller.appspotmail.com
>> Closes: https://lore.kernel.org/linux-f2fs-devel/674f4e7d.050a0220.17bd51.004f.GAE@google.com
>> Signed-off-by: Chao Yu <chao@...nel.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?

Thanks for fixing.

I'd like to fix this in v2, meanwhile including more information from Qasdev's
patch.

Thanks,

>> +			  __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