[PATCH] btrfs: fix error value in btrfs_get_extent

[PATCH] btrfs: fix error value in btrfs_get_extent

[Pavel Machek]

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btrfs_get_extent() sets variable ret, but out: error path expect error
to be in variable err. Fix that.

Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>

---

Notice that patch introducing this problem is on its way to 4.19.137-stable.

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 7befb7c12bd3..4aaa01540f89 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7012,7 +7012,7 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 	    found_type == BTRFS_FILE_EXTENT_PREALLOC) {
 		/* Only regular file could have regular/prealloc extent */
 		if (!S_ISREG(inode->vfs_inode.i_mode)) {
-			ret = -EUCLEAN;
+			err = -EUCLEAN;
 			btrfs_crit(fs_info,
 		"regular/prealloc extent found for non-regular inode %llu",
 				   btrfs_ino(inode));

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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Re: [PATCH] btrfs: fix error value in btrfs_get_extent

[Nikolay Borisov]

On 3.08.20 г. 12:35 ч., Pavel Machek wrote:
> btrfs_get_extent() sets variable ret, but out: error path expect error
> to be in variable err. Fix that.
> 
> Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>

Good catch, this also needs:

Fixes: 6bf9e4bd6a27 ("btrfs: inode: Verify inode mode to avoid NULL
pointer dereference")

Reviewed-by: Nikolay Borisov <nborisov@suse.com>


> 
> ---
> 
> Notice that patch introducing this problem is on its way to 4.19.137-stable.
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 7befb7c12bd3..4aaa01540f89 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -7012,7 +7012,7 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
>  	    found_type == BTRFS_FILE_EXTENT_PREALLOC) {
>  		/* Only regular file could have regular/prealloc extent */
>  		if (!S_ISREG(inode->vfs_inode.i_mode)) {
> -			ret = -EUCLEAN;
> +			err = -EUCLEAN;
>  			btrfs_crit(fs_info,
>  		"regular/prealloc extent found for non-regular inode %llu",
>  				   btrfs_ino(inode));
> 

Re: [PATCH] btrfs: fix error value in btrfs_get_extent

[Nikolay Borisov]

On 3.08.20 г. 12:39 ч., Nikolay Borisov wrote:
> 
> 
> On 3.08.20 г. 12:35 ч., Pavel Machek wrote:
>> btrfs_get_extent() sets variable ret, but out: error path expect error
>> to be in variable err. Fix that.
>>
>> Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>
> 
> Good catch, this also needs:
> 
> Fixes: 6bf9e4bd6a27 ("btrfs: inode: Verify inode mode to avoid NULL
> pointer dereference")
> 
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>

Actually the reason this error got introduced in the first place and I
missed it during the review is that the function is doing something
rather counter-intuitive - it's using 'err' variable as a synonym for
'ret'. A better approach would be to simply remove 'err' from that
function. I'm now authoring such a patch, nevertheless the issue still
stands.

> 
> 
>>
>> ---
>>
>> Notice that patch introducing this problem is on its way to 4.19.137-stable.
>>
>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>> index 7befb7c12bd3..4aaa01540f89 100644
>> --- a/fs/btrfs/inode.c
>> +++ b/fs/btrfs/inode.c
>> @@ -7012,7 +7012,7 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
>>  	    found_type == BTRFS_FILE_EXTENT_PREALLOC) {
>>  		/* Only regular file could have regular/prealloc extent */
>>  		if (!S_ISREG(inode->vfs_inode.i_mode)) {
>> -			ret = -EUCLEAN;
>> +			err = -EUCLEAN;
>>  			btrfs_crit(fs_info,
>>  		"regular/prealloc extent found for non-regular inode %llu",
>>  				   btrfs_ino(inode));
>>
> 

Re: [PATCH] btrfs: fix error value in btrfs_get_extent

[David Sterba]

On Mon, Aug 03, 2020 at 11:35:06AM +0200, Pavel Machek wrote:
> btrfs_get_extent() sets variable ret, but out: error path expect error
> to be in variable err. Fix that.
> 
> Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>

Thanks, patch queued for 5.9.
> 
> ---
> 
> Notice that patch introducing this problem is on its way to 4.19.137-stable.

Yeah, I'll let stable team know once this patch gets merged that the
relevant patches can be picked.

Re: [PATCH] btrfs: fix error value in btrfs_get_extent

[David Sterba]

On Mon, Aug 03, 2020 at 12:50:31PM +0300, Nikolay Borisov wrote:
> On 3.08.20 г. 12:39 ч., Nikolay Borisov wrote:
> > On 3.08.20 г. 12:35 ч., Pavel Machek wrote:
> >> btrfs_get_extent() sets variable ret, but out: error path expect error
> >> to be in variable err. Fix that.
> >>
> >> Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>
> > 
> > Good catch, this also needs:
> > 
> > Fixes: 6bf9e4bd6a27 ("btrfs: inode: Verify inode mode to avoid NULL
> > pointer dereference")
> > 
> > Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> 
> Actually the reason this error got introduced in the first place and I
> missed it during the review is that the function is doing something
> rather counter-intuitive - it's using 'err' variable as a synonym for
> 'ret'. A better approach would be to simply remove 'err' from that
> function. I'm now authoring such a patch, nevertheless the issue still
> stands.

The expected pattern is to use 'ret' for function return value and add
other temporary variables instead of the err/ret switching, which can be
found in the oldish code still. So the cleanup is going to do the right
thing, thanks.