linux-kernel - Re: [PATCH 5.10 60/76] f2fs: fix to do sanity check on last xattr entry in __f2fs

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Date:   Tue, 4 Jan 2022 17:29:30 +0800
From:   Chao Yu <chao@...nel.org>
To:     Salvatore Bonaccorso <carnil@...ian.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Wenqing Liu <wenqingliu0120@...il.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>
Subject: Re: [PATCH 5.10 60/76] f2fs: fix to do sanity check on last xattr
 entry in __f2fs_setxattr()

On 2022/1/4 5:11, Salvatore Bonaccorso wrote:
> Hi,
> 
> On Mon, Dec 27, 2021 at 04:31:15PM +0100, Greg Kroah-Hartman wrote:
>> From: Chao Yu <chao@...nel.org>
>>
>> commit 5598b24efaf4892741c798b425d543e4bed357a1 upstream.

I've no idea.

I didn't add this line from v1 to v3:

https://lore.kernel.org/lkml/20211211154059.7173-1-chao@kernel.org/T/
https://lore.kernel.org/all/20211212071923.2398-1-chao@kernel.org/T/
https://lore.kernel.org/all/20211212091630.6325-1-chao@kernel.org/T/

Am I missing anything?

Thanks,

>>
>> As Wenqing Liu reported in bugzilla:
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=215235
>>
>> - Overview
>> page fault in f2fs_setxattr() when mount and operate on corrupted image
>>
>> - Reproduce
>> tested on kernel 5.16-rc3, 5.15.X under root
>>
>> 1. unzip tmp7.zip
>> 2. ./single.sh f2fs 7
>>
>> Sometimes need to run the script several times
>>
>> - Kernel dump
>> loop0: detected capacity change from 0 to 131072
>> F2FS-fs (loop0): Found nat_bits in checkpoint
>> F2FS-fs (loop0): Mounted with checkpoint version = 7548c2ee
>> BUG: unable to handle page fault for address: ffffe47bc7123f48
>> RIP: 0010:kfree+0x66/0x320
>> Call Trace:
>>   __f2fs_setxattr+0x2aa/0xc00 [f2fs]
>>   f2fs_setxattr+0xfa/0x480 [f2fs]
>>   __f2fs_set_acl+0x19b/0x330 [f2fs]
>>   __vfs_removexattr+0x52/0x70
>>   __vfs_removexattr_locked+0xb1/0x140
>>   vfs_removexattr+0x56/0x100
>>   removexattr+0x57/0x80
>>   path_removexattr+0xa3/0xc0
>>   __x64_sys_removexattr+0x17/0x20
>>   do_syscall_64+0x37/0xb0
>>   entry_SYSCALL_64_after_hwframe+0x44/0xae
>>
>> The root cause is in __f2fs_setxattr(), we missed to do sanity check on
>> last xattr entry, result in out-of-bound memory access during updating
>> inconsistent xattr data of target inode.
>>
>> After the fix, it can detect such xattr inconsistency as below:
>>
>> F2FS-fs (loop11): inode (7) has invalid last xattr entry, entry_size: 60676
>> F2FS-fs (loop11): inode (8) has corrupted xattr
>> F2FS-fs (loop11): inode (8) has corrupted xattr
>> F2FS-fs (loop11): inode (8) has invalid last xattr entry, entry_size: 47736
>>
>> Cc: stable@...r.kernel.org
>> Reported-by: Wenqing Liu <wenqingliu0120@...il.com>
>> Signed-off-by: Chao Yu <chao@...nel.org>
>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> ---
>>   fs/f2fs/xattr.c |   11 ++++++++++-
>>   1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> --- a/fs/f2fs/xattr.c
>> +++ b/fs/f2fs/xattr.c
>> @@ -680,8 +680,17 @@ static int __f2fs_setxattr(struct inode
>>   	}
>>   
>>   	last = here;
>> -	while (!IS_XATTR_LAST_ENTRY(last))
>> +	while (!IS_XATTR_LAST_ENTRY(last)) {
>> +		if ((void *)(last) + sizeof(__u32) > last_base_addr ||
>> +			(void *)XATTR_NEXT_ENTRY(last) > last_base_addr) {
>> +			f2fs_err(F2FS_I_SB(inode), "inode (%lu) has invalid last xattr entry, entry_size: %zu",
>> +					inode->i_ino, ENTRY_SIZE(last));
>> +			set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
>> +			error = -EFSCORRUPTED;
>> +			goto exit;
>> +		}
>>   		last = XATTR_NEXT_ENTRY(last);
>> +	}
>>   
>>   	newsize = XATTR_ALIGN(sizeof(struct f2fs_xattr_entry) + len + size);
> 
> It looks this commit while it was applied to several stable series
> (TTBOMK in 5.15.12, 5.10.89, 5.4.169, 4.19.223 and 4.14.260) it is
> still missing from mainline, Chao, or anyone else, do you know what
> happened here?
> 
> Regards,
> Salvatore