[01/11] ext4: Fix xattr shifting when expanding inodes

The code in ext4_expand_extra_isize_ea() treated new_extra_isize
argument sometimes as the desired target i_extra_isize and sometimes as
the amount by which we need to grow current i_extra_isize. These happen
to coincide when i_extra_isize is 0 which used to be the common case and
so nobody noticed this until recently when we added i_projid to the
inode and so i_extra_isize now needs to grow from 28 to 32 bytes.

The result of these bugs was that we sometimes unnecessarily decided to
move xattrs out of inode even if there was enough space and we often
ended up corrupting in-inode xattrs because arguments to
ext4_xattr_shift_entries() were just wrong. This could demonstrate
itself as BUG_ON in ext4_xattr_shift_entries() triggering.

Fix the problem by introducing new isize_diff variable and use it where
appropriate.

CC: <stable@vger.kernel.org> # 4.4.x-
Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/xattr.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

On Aug 3, 2016, at 4:39 AM, Jan Kara <jack@suse.cz> wrote:
> 
> The code in ext4_expand_extra_isize_ea() treated new_extra_isize
> argument sometimes as the desired target i_extra_isize and sometimes as
> the amount by which we need to grow current i_extra_isize. These happen
> to coincide when i_extra_isize is 0 which used to be the common case and
> so nobody noticed this until recently when we added i_projid to the
> inode and so i_extra_isize now needs to grow from 28 to 32 bytes.
> 
> The result of these bugs was that we sometimes unnecessarily decided to
> move xattrs out of inode even if there was enough space and we often
> ended up corrupting in-inode xattrs because arguments to
> ext4_xattr_shift_entries() were just wrong. This could demonstrate
> itself as BUG_ON in ext4_xattr_shift_entries() triggering.
> 
> Fix the problem by introducing new isize_diff variable and use it where
> appropriate.
> 
> CC: <stable@vger.kernel.org> # 4.4.x-
> Reported-by: Dave Chinner <david@fromorbit.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> fs/ext4/xattr.c | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> index 39e9cfb1b371..cb1d7b4482de 100644
> --- a/fs/ext4/xattr.c
> +++ b/fs/ext4/xattr.c
> @@ -1353,11 +1353,13 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
> 	size_t min_offs, free;
> 	int total_ino;
> 	void *base, *start, *end;
> -	int extra_isize = 0, error = 0, tried_min_extra_isize = 0;
> +	int error = 0, tried_min_extra_isize = 0;
> 	int s_min_extra_isize = le16_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_min_extra_isize);
> +	int isize_diff;	/* How much do we need to grow i_extra_isize */
> 
> 	down_write(&EXT4_I(inode)->xattr_sem);
> retry:
> +	isize_diff = new_extra_isize - EXT4_I(inode)->i_extra_isize;
> 	if (EXT4_I(inode)->i_extra_isize >= new_extra_isize) {

Not a big deal, but either the isize_diff calculation could be moved
after the "if () {}" block, or the condition could be changed to:

	if (isize_diff <= 0) {

since isize_diff is otherwise unused if this condition is true.

You can add my

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

Cheers, Andreas

> 		up_write(&EXT4_I(inode)->xattr_sem);
> 		return 0;
> @@ -1382,7 +1384,7 @@ retry:
> 		goto cleanup;
> 
> 	free = ext4_xattr_free_space(last, &min_offs, base, &total_ino);
> -	if (free >= new_extra_isize) {
> +	if (free >= isize_diff) {
> 		entry = IFIRST(header);
> 		ext4_xattr_shift_entries(entry,	EXT4_I(inode)->i_extra_isize
> 				- new_extra_isize, (void *)raw_inode +
> @@ -1414,7 +1416,7 @@ retry:
> 		end = bh->b_data + bh->b_size;
> 		min_offs = end - base;
> 		free = ext4_xattr_free_space(first, &min_offs, base, NULL);
> -		if (free < new_extra_isize) {
> +		if (free < isize_diff) {
> 			if (!tried_min_extra_isize && s_min_extra_isize) {
> 				tried_min_extra_isize++;
> 				new_extra_isize = s_min_extra_isize;
> @@ -1428,7 +1430,7 @@ retry:
> 		free = inode->i_sb->s_blocksize;
> 	}
> 
> -	while (new_extra_isize > 0) {
> +	while (isize_diff > 0) {
> 		size_t offs, size, entry_size;
> 		struct ext4_xattr_entry *small_entry = NULL;
> 		struct ext4_xattr_info i = {
> @@ -1459,7 +1461,7 @@ retry:
> 			EXT4_XATTR_SIZE(le32_to_cpu(last->e_value_size)) +
> 					EXT4_XATTR_LEN(last->e_name_len);
> 			if (total_size <= free && total_size < min_total_size) {
> -				if (total_size < new_extra_isize) {
> +				if (total_size < isize_diff) {
> 					small_entry = last;
> 				} else {
> 					entry = last;
> @@ -1516,20 +1518,19 @@ retry:
> 			goto cleanup;
> 
> 		entry = IFIRST(header);
> -		if (entry_size + EXT4_XATTR_SIZE(size) >= new_extra_isize)
> -			shift_bytes = new_extra_isize;
> +		if (entry_size + EXT4_XATTR_SIZE(size) >= isize_diff)
> +			shift_bytes = isize_diff;
> 		else
> 			shift_bytes = entry_size + size;
> 		/* Adjust the offsets and shift the remaining entries ahead */
> -		ext4_xattr_shift_entries(entry, EXT4_I(inode)->i_extra_isize -
> -			shift_bytes, (void *)raw_inode +
> -			EXT4_GOOD_OLD_INODE_SIZE + extra_isize + shift_bytes,
> +		ext4_xattr_shift_entries(entry, -shift_bytes,
> +			(void *)raw_inode + EXT4_GOOD_OLD_INODE_SIZE +
> +			EXT4_I(inode)->i_extra_isize + shift_bytes,
> 			(void *)header, total_ino - entry_size,
> 			inode->i_sb->s_blocksize);
> 
> -		extra_isize += shift_bytes;
> -		new_extra_isize -= shift_bytes;
> -		EXT4_I(inode)->i_extra_isize = extra_isize;
> +		isize_diff -= shift_bytes;
> +		EXT4_I(inode)->i_extra_isize += shift_bytes;
> 
> 		i.name = b_entry_name;
> 		i.value = buffer;
> --
> 2.6.6
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


Cheers, Andreas

On Wed 03-08-16 17:25:58, Andreas Dilger wrote:
> On Aug 3, 2016, at 4:39 AM, Jan Kara <jack@suse.cz> wrote:
> > 
> > The code in ext4_expand_extra_isize_ea() treated new_extra_isize
> > argument sometimes as the desired target i_extra_isize and sometimes as
> > the amount by which we need to grow current i_extra_isize. These happen
> > to coincide when i_extra_isize is 0 which used to be the common case and
> > so nobody noticed this until recently when we added i_projid to the
> > inode and so i_extra_isize now needs to grow from 28 to 32 bytes.
> > 
> > The result of these bugs was that we sometimes unnecessarily decided to
> > move xattrs out of inode even if there was enough space and we often
> > ended up corrupting in-inode xattrs because arguments to
> > ext4_xattr_shift_entries() were just wrong. This could demonstrate
> > itself as BUG_ON in ext4_xattr_shift_entries() triggering.
> > 
> > Fix the problem by introducing new isize_diff variable and use it where
> > appropriate.
> > 
> > CC: <stable@vger.kernel.org> # 4.4.x-
> > Reported-by: Dave Chinner <david@fromorbit.com>
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> > fs/ext4/xattr.c | 27 ++++++++++++++-------------
> > 1 file changed, 14 insertions(+), 13 deletions(-)
> > 
> > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
> > index 39e9cfb1b371..cb1d7b4482de 100644
> > --- a/fs/ext4/xattr.c
> > +++ b/fs/ext4/xattr.c
> > @@ -1353,11 +1353,13 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
> > 	size_t min_offs, free;
> > 	int total_ino;
> > 	void *base, *start, *end;
> > -	int extra_isize = 0, error = 0, tried_min_extra_isize = 0;
> > +	int error = 0, tried_min_extra_isize = 0;
> > 	int s_min_extra_isize = le16_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_min_extra_isize);
> > +	int isize_diff;	/* How much do we need to grow i_extra_isize */
> > 
> > 	down_write(&EXT4_I(inode)->xattr_sem);
> > retry:
> > +	isize_diff = new_extra_isize - EXT4_I(inode)->i_extra_isize;
> > 	if (EXT4_I(inode)->i_extra_isize >= new_extra_isize) {
> 
> Not a big deal, but either the isize_diff calculation could be moved
> after the "if () {}" block, or the condition could be changed to:
> 
> 	if (isize_diff <= 0) {
> 
> since isize_diff is otherwise unused if this condition is true.
> 
> You can add my
> 
> Reviewed-by: Andreas Dilger <adilger@dilger.ca>

Thanks for review. Yes, my plan was to use isize_diff in couple more places
in the function (including the following condition) but I didn't want to
introduce unnecessary churn in these initial patches for stable kernel. It
seems I forgot to do this in the followup cleanup patches but I guess it's
not worth a respin now. If there are more comments, I'll include this as
well.

								Honza

On Wed, Aug 03, 2016 at 12:39:45PM +0200, Jan Kara wrote:
> The code in ext4_expand_extra_isize_ea() treated new_extra_isize
> argument sometimes as the desired target i_extra_isize and sometimes as
> the amount by which we need to grow current i_extra_isize. These happen
> to coincide when i_extra_isize is 0 which used to be the common case and
> so nobody noticed this until recently when we added i_projid to the
> inode and so i_extra_isize now needs to grow from 28 to 32 bytes.
> 
> The result of these bugs was that we sometimes unnecessarily decided to
> move xattrs out of inode even if there was enough space and we often
> ended up corrupting in-inode xattrs because arguments to
> ext4_xattr_shift_entries() were just wrong. This could demonstrate
> itself as BUG_ON in ext4_xattr_shift_entries() triggering.
> 
> Fix the problem by introducing new isize_diff variable and use it where
> appropriate.
> 
> CC: <stable@vger.kernel.org> # 4.4.x-
> Reported-by: Dave Chinner <david@fromorbit.com>
> Signed-off-by: Jan Kara <jack@suse.cz>

Thanks, applied.

					- Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html