[EXT4 set 2][PATCH 2/5] cleanups: Add extent sanity checks

[EXT4 set 2][PATCH 2/5] cleanups: Add extent sanity checks

[Mingming Cao]

with the patch all headers are checked. the code should become
more resistant to on-disk corruptions. needless BUG_ON() have
been removed. please, review for inclusion.

Signed-off-by: Alex Tomas <alex@clusterfs.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>

Index: linux-2.6.22-rc4/fs/ext4/extents.c
===================================================================
--- linux-2.6.22-rc4.orig/fs/ext4/extents.c	2007-06-11 17:22:15.000000000 -0700
+++ linux-2.6.22-rc4/fs/ext4/extents.c	2007-06-11 17:27:57.000000000 -0700
@@ -91,36 +91,6 @@
 	ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 0xffff);
 }
 
-static int ext4_ext_check_header(const char *function, struct inode *inode,
-				struct ext4_extent_header *eh)
-{
-	const char *error_msg = NULL;
-
-	if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
-		error_msg = "invalid magic";
-		goto corrupted;
-	}
-	if (unlikely(eh->eh_max == 0)) {
-		error_msg = "invalid eh_max";
-		goto corrupted;
-	}
-	if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
-		error_msg = "invalid eh_entries";
-		goto corrupted;
-	}
-	return 0;
-
-corrupted:
-	ext4_error(inode->i_sb, function,
-			"bad header in inode #%lu: %s - magic %x, "
-			"entries %u, max %u, depth %u",
-			inode->i_ino, error_msg, le16_to_cpu(eh->eh_magic),
-			le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
-			le16_to_cpu(eh->eh_depth));
-
-	return -EIO;
-}
-
 static handle_t *ext4_ext_journal_restart(handle_t *handle, int needed)
 {
 	int err;
@@ -269,6 +239,70 @@
 	return size;
 }
 
+static inline int
+ext4_ext_max_entries(struct inode *inode, int depth)
+{
+	int max;
+
+	if (depth == ext_depth(inode)) {
+		if (depth == 0)
+			max = ext4_ext_space_root(inode);
+		else
+			max = ext4_ext_space_root_idx(inode);
+	} else {
+		if (depth == 0)
+			max = ext4_ext_space_block(inode);
+		else
+			max = ext4_ext_space_block_idx(inode);
+	}
+
+	return max;
+}
+
+static int __ext4_ext_check_header(const char *function, struct inode *inode,
+					struct ext4_extent_header *eh,
+					int depth)
+{
+	const char *error_msg = NULL;
+	int max = 0;
+
+	if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
+		error_msg = "invalid magic";
+		goto corrupted;
+	}
+	if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
+		error_msg = "unexpected eh_depth";
+		goto corrupted;
+	}
+	if (unlikely(eh->eh_max == 0)) {
+		error_msg = "invalid eh_max";
+		goto corrupted;
+	}
+	max = ext4_ext_max_entries(inode, depth);
+	if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
+		error_msg = "too large eh_max";
+		goto corrupted;
+	}
+	if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
+		error_msg = "invalid eh_entries";
+		goto corrupted;
+	}
+	return 0;
+
+corrupted:
+	ext4_error(inode->i_sb, function,
+			"bad header in inode #%lu: %s - magic %x, "
+			"entries %u, max %u(%u), depth %u(%u)",
+			inode->i_ino, error_msg, le16_to_cpu(eh->eh_magic),
+			le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
+			max, le16_to_cpu(eh->eh_depth), depth);
+
+	return -EIO;
+}
+
+#define ext4_ext_check_header(inode, eh, depth)	\
+	__ext4_ext_check_header(__FUNCTION__, inode, eh, depth)
+
 #ifdef EXT_DEBUG
 static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
 {
@@ -329,6 +363,7 @@
 /*
  * ext4_ext_binsearch_idx:
  * binary search for the closest index of the given block
+ * the header must be checked before calling this
  */
 static void
 ext4_ext_binsearch_idx(struct inode *inode, struct ext4_ext_path *path, int block)
@@ -336,9 +371,6 @@
 	struct ext4_extent_header *eh = path->p_hdr;
 	struct ext4_extent_idx *r, *l, *m;
 
-	BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);
-	BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));
-	BUG_ON(le16_to_cpu(eh->eh_entries) <= 0);
 
 	ext_debug("binsearch for %d(idx):  ", block);
 
@@ -388,6 +420,7 @@
 /*
  * ext4_ext_binsearch:
  * binary search for closest extent of the given block
+ * the header must be checked before calling this
  */
 static void
 ext4_ext_binsearch(struct inode *inode, struct ext4_ext_path *path, int block)
@@ -395,9 +428,6 @@
 	struct ext4_extent_header *eh = path->p_hdr;
 	struct ext4_extent *r, *l, *m;
 
-	BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);
-	BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));
-
 	if (eh->eh_entries == 0) {
 		/*
 		 * this leaf is empty:
@@ -468,11 +498,10 @@
 	short int depth, i, ppos = 0, alloc = 0;
 
 	eh = ext_inode_hdr(inode);
-	BUG_ON(eh == NULL);
-	if (ext4_ext_check_header(__FUNCTION__, inode, eh))
+	i = depth = ext_depth(inode);
+	if (ext4_ext_check_header(inode, eh, depth))
 		return ERR_PTR(-EIO);
 
-	i = depth = ext_depth(inode);
 
 	/* account possible depth increase */
 	if (!path) {
@@ -488,6 +517,7 @@
 	while (i) {
 		ext_debug("depth %d: num %d, max %d\n",
 			  ppos, le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
+
 		ext4_ext_binsearch_idx(inode, path + ppos, block);
 		path[ppos].p_block = idx_pblock(path[ppos].p_idx);
 		path[ppos].p_depth = i;
@@ -504,7 +534,7 @@
 		path[ppos].p_hdr = eh;
 		i--;
 
-		if (ext4_ext_check_header(__FUNCTION__, inode, eh))
+		if (ext4_ext_check_header(inode, eh, i))
 			goto err;
 	}
 
@@ -513,9 +543,6 @@
 	path[ppos].p_ext = NULL;
 	path[ppos].p_idx = NULL;
 
-	if (ext4_ext_check_header(__FUNCTION__, inode, eh))
-		goto err;
-
 	/* find extent */
 	ext4_ext_binsearch(inode, path + ppos, block);
 
@@ -1673,13 +1700,12 @@
 	unsigned short ex_ee_len;
 	struct ext4_extent *ex;
 
+	/* the header must be checked already in ext4_ext_remove_space() */
 	ext_debug("truncate since %lu in leaf\n", start);
 	if (!path[depth].p_hdr)
 		path[depth].p_hdr = ext_block_hdr(path[depth].p_bh);
 	eh = path[depth].p_hdr;
 	BUG_ON(eh == NULL);
-	BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));
-	BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);
 
 	/* find where to start removing */
 	ex = EXT_LAST_EXTENT(eh);
@@ -1825,7 +1851,7 @@
 		return -ENOMEM;
 	}
 	path[0].p_hdr = ext_inode_hdr(inode);
-	if (ext4_ext_check_header(__FUNCTION__, inode, path[0].p_hdr)) {
+	if (ext4_ext_check_header(inode, path[0].p_hdr, depth)) {
 		err = -EIO;
 		goto out;
 	}
@@ -1846,17 +1872,8 @@
 		if (!path[i].p_hdr) {
 			ext_debug("initialize header\n");
 			path[i].p_hdr = ext_block_hdr(path[i].p_bh);
-			if (ext4_ext_check_header(__FUNCTION__, inode,
-							path[i].p_hdr)) {
-				err = -EIO;
-				goto out;
-			}
 		}
 
-		BUG_ON(le16_to_cpu(path[i].p_hdr->eh_entries)
-			   > le16_to_cpu(path[i].p_hdr->eh_max));
-		BUG_ON(path[i].p_hdr->eh_magic != EXT4_EXT_MAGIC);
-
 		if (!path[i].p_idx) {
 			/* this level hasn't been touched yet */
 			path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
@@ -1873,17 +1890,24 @@
 				i, EXT_FIRST_INDEX(path[i].p_hdr),
 				path[i].p_idx);
 		if (ext4_ext_more_to_rm(path + i)) {
+			struct buffer_head *bh;
 			/* go to the next level */
 			ext_debug("move to level %d (block %llu)\n",
 				  i + 1, idx_pblock(path[i].p_idx));
 			memset(path + i + 1, 0, sizeof(*path));
-			path[i+1].p_bh =
-				sb_bread(sb, idx_pblock(path[i].p_idx));
-			if (!path[i+1].p_bh) {
+			bh = sb_bread(sb, idx_pblock(path[i].p_idx));
+			if (!bh) {
 				/* should we reset i_size? */
 				err = -EIO;
 				break;
 			}
+			BUG_ON(i + 1 > depth);
+			if (ext4_ext_check_header(inode, ext_block_hdr(bh),
+							depth - i - 1)) {
+				err = -EIO;
+				break;
+			}
+			path[i+1].p_bh = bh;
 
 			/* save actual number of indexes since this
 			 * number is changed at the next iteration */

Re: [EXT4 set 2][PATCH 2/5] cleanups: Add extent sanity checks

[Andrew Morton]

On Sun, 01 Jul 2007 03:36:22 -0400
Mingming Cao <cmm@us.ibm.com> wrote:

> with the patch all headers are checked. the code should become
> more resistant to on-disk corruptions. needless BUG_ON() have
> been removed. please, review for inclusion.
> 
> ...

> @@ -269,6 +239,70 @@
>  	return size;
>  }
>  
> +static inline int
> +ext4_ext_max_entries(struct inode *inode, int depth)

Please remove the `inline'.

`inline' is usually wrong.  It is wrong here.  If this function has a
single callsite (it has) then the compiler will inline it.  If the function
later gains more callsites then the compiler will know (correctly) not to
inline it.

We hope.  If we find the compiler still inlines a function as large as this
one then we'd need to use noinline and complain at the gcc developers.

> +{
> +	int max;
> +
> +	if (depth == ext_depth(inode)) {
> +		if (depth == 0)
> +			max = ext4_ext_space_root(inode);
> +		else
> +			max = ext4_ext_space_root_idx(inode);
> +	} else {
> +		if (depth == 0)
> +			max = ext4_ext_space_block(inode);
> +		else
> +			max = ext4_ext_space_block_idx(inode);
> +	}
> +
> +	return max;
> +}
> +
> +static int __ext4_ext_check_header(const char *function, struct inode *inode,
> +					struct ext4_extent_header *eh,
> +					int depth)
> +{
> +	const char *error_msg = NULL;

Unneeded initialisation.

> +	int max = 0;
> +
> +	if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
> +		error_msg = "invalid magic";
> +		goto corrupted;
> +	}
> +	if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
> +		error_msg = "unexpected eh_depth";
> +		goto corrupted;
> +	}
> +	if (unlikely(eh->eh_max == 0)) {
> +		error_msg = "invalid eh_max";
> +		goto corrupted;
> +	}
> +	max = ext4_ext_max_entries(inode, depth);
> +	if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
> +		error_msg = "too large eh_max";
> +		goto corrupted;
> +	}
> +	if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
> +		error_msg = "invalid eh_entries";
> +		goto corrupted;
> +	}
> +	return 0;
> +
> +corrupted:
> +	ext4_error(inode->i_sb, function,
> +			"bad header in inode #%lu: %s - magic %x, "
> +			"entries %u, max %u(%u), depth %u(%u)",
> +			inode->i_ino, error_msg, le16_to_cpu(eh->eh_magic),
> +			le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
> +			max, le16_to_cpu(eh->eh_depth), depth);
> +
> +	return -EIO;
> +}
> +
>
> ...
>
> +	i = depth = ext_depth(inode);
>

Mulitple assignments like this are somewhat unpopular from the coding-style
POV.  

We have a local variable called `i' which is not used as a simple counter
and which has no explanatory comment.  This is plain bad.  Please find a
better name for this variable.  Review the code for other such lack of
clarity - I'm sure there's more.


> -	BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));
> -	BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);

Yeah, this patch improves things a lot.

How well-tested is it?  Have any of these errors actually been triggered?

>  			path[i].p_hdr = ext_block_hdr(path[i].p_bh);
> -			if (ext4_ext_check_header(__FUNCTION__, inode,
> -							path[i].p_hdr)) {
> -				err = -EIO;
> -				goto out;
> -			}
>  		}
>  
> -		BUG_ON(le16_to_cpu(path[i].p_hdr->eh_entries)
> -			   > le16_to_cpu(path[i].p_hdr->eh_max));
> -		BUG_ON(path[i].p_hdr->eh_magic != EXT4_EXT_MAGIC);
> -
>  		if (!path[i].p_idx) {
>  			/* this level hasn't been touched yet */
>  			path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
> @@ -1873,17 +1890,24 @@
>  				i, EXT_FIRST_INDEX(path[i].p_hdr),
>  				path[i].p_idx);
>  		if (ext4_ext_more_to_rm(path + i)) {
> +			struct buffer_head *bh;
>  			/* go to the next level */
>  			ext_debug("move to level %d (block %llu)\n",
>  				  i + 1, idx_pblock(path[i].p_idx));
>  			memset(path + i + 1, 0, sizeof(*path));
> -			path[i+1].p_bh =
> -				sb_bread(sb, idx_pblock(path[i].p_idx));
> -			if (!path[i+1].p_bh) {
> +			bh = sb_bread(sb, idx_pblock(path[i].p_idx));
> +			if (!bh) {
>  				/* should we reset i_size? */
>  				err = -EIO;
>  				break;
>  			}
> +			BUG_ON(i + 1 > depth);

ouch.  Couldn't we do WARN_ON then return -EIO here?

> +			if (ext4_ext_check_header(inode, ext_block_hdr(bh),
> +							depth - i - 1)) {
> +				err = -EIO;
> +				break;
> +			}
> +			path[i+1].p_bh = bh;

Really that should have been "i + 1".  checkpatch misses this.  It seems to
be missing more stuff that it used to lately.

Re: [EXT4 set 2][PATCH 2/5] cleanups: Add extent sanity checks

[Mingming Cao]

On Tue, 2007-07-10 at 16:30 -0700, Andrew Morton wrote:
> On Sun, 01 Jul 2007 03:36:22 -0400
> Mingming Cao <cmm@us.ibm.com> wrote:
> 
> > with the patch all headers are checked. the code should become
> > more resistant to on-disk corruptions. needless BUG_ON() have
> > been removed. please, review for inclusion.
> > 
> > ...
> 
> > @@ -269,6 +239,70 @@
> >  	return size;
> >  }
> >  
> > +static inline int
> > +ext4_ext_max_entries(struct inode *inode, int depth)
> 
> Please remove the `inline'.
> 
done
> `inline' is usually wrong.  It is wrong here.  If this function has a
> single callsite (it has) then the compiler will inline it.  If the function
> later gains more callsites then the compiler will know (correctly) not to
> inline it.
> 
> We hope.  If we find the compiler still inlines a function as large as this
> one then we'd need to use noinline and complain at the gcc developers.
> 
> > +{
> > +	int max;
> > +
> > +	if (depth == ext_depth(inode)) {
> > +		if (depth == 0)
> > +			max = ext4_ext_space_root(inode);
> > +		else
> > +			max = ext4_ext_space_root_idx(inode);
> > +	} else {
> > +		if (depth == 0)
> > +			max = ext4_ext_space_block(inode);
> > +		else
> > +			max = ext4_ext_space_block_idx(inode);
> > +	}
> > +
> > +	return max;
> > +}
> > +
> > +static int __ext4_ext_check_header(const char *function, struct inode *inode,
> > +					struct ext4_extent_header *eh,
> > +					int depth)
> > +{
> > +	const char *error_msg = NULL;
> 
> Unneeded initialisation.
> 
done

> > +	int max = 0;
> > +
> > +	if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
> > +		error_msg = "invalid magic";
> > +		goto corrupted;
> > +	}
> > +	if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
> > +		error_msg = "unexpected eh_depth";
> > +		goto corrupted;
> > +	}
> > +	if (unlikely(eh->eh_max == 0)) {
> > +		error_msg = "invalid eh_max";
> > +		goto corrupted;
> > +	}
> > +	max = ext4_ext_max_entries(inode, depth);
> > +	if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
> > +		error_msg = "too large eh_max";
> > +		goto corrupted;
> > +	}
> > +	if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
> > +		error_msg = "invalid eh_entries";
> > +		goto corrupted;
> > +	}
> > +	return 0;
> > +
> > +corrupted:
> > +	ext4_error(inode->i_sb, function,
> > +			"bad header in inode #%lu: %s - magic %x, "
> > +			"entries %u, max %u(%u), depth %u(%u)",
> > +			inode->i_ino, error_msg, le16_to_cpu(eh->eh_magic),
> > +			le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
> > +			max, le16_to_cpu(eh->eh_depth), depth);
> > +
> > +	return -EIO;
> > +}
> > +
> >
> > ...
> >
> > +	i = depth = ext_depth(inode);
> >
> 
> Mulitple assignments like this are somewhat unpopular from the coding-style
> POV.  
> 
okay.

> We have a local variable called `i' which is not used as a simple counter
> and which has no explanatory comment.  This is plain bad.  Please find a
> better name for this variable.  Review the code for other such lack of
> clarity - I'm sure there's more.
> 
"i" is is loop counter. I have moved the i= depth to before the while
loop.

> 
> > -	BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));
> > -	BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);
> 
> Yeah, this patch improves things a lot.
> 
> How well-tested is it?  Have any of these errors actually been triggered?
> 
> >  			path[i].p_hdr = ext_block_hdr(path[i].p_bh);
> > -			if (ext4_ext_check_header(__FUNCTION__, inode,
> > -							path[i].p_hdr)) {
> > -				err = -EIO;
> > -				goto out;
> > -			}
> >  		}
> >  
> > -		BUG_ON(le16_to_cpu(path[i].p_hdr->eh_entries)
> > -			   > le16_to_cpu(path[i].p_hdr->eh_max));
> > -		BUG_ON(path[i].p_hdr->eh_magic != EXT4_EXT_MAGIC);
> > -
> >  		if (!path[i].p_idx) {
> >  			/* this level hasn't been touched yet */
> >  			path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
> > @@ -1873,17 +1890,24 @@
> >  				i, EXT_FIRST_INDEX(path[i].p_hdr),
> >  				path[i].p_idx);
> >  		if (ext4_ext_more_to_rm(path + i)) {
> > +			struct buffer_head *bh;
> >  			/* go to the next level */
> >  			ext_debug("move to level %d (block %llu)\n",
> >  				  i + 1, idx_pblock(path[i].p_idx));
> >  			memset(path + i + 1, 0, sizeof(*path));
> > -			path[i+1].p_bh =
> > -				sb_bread(sb, idx_pblock(path[i].p_idx));
> > -			if (!path[i+1].p_bh) {
> > +			bh = sb_bread(sb, idx_pblock(path[i].p_idx));
> > +			if (!bh) {
> >  				/* should we reset i_size? */
> >  				err = -EIO;
> >  				break;
> >  			}
> > +			BUG_ON(i + 1 > depth);
> 
> ouch.  Couldn't we do WARN_ON then return -EIO here?

Done
> 
> > +			if (ext4_ext_check_header(inode, ext_block_hdr(bh),
> > +							depth - i - 1)) {
> > +				err = -EIO;
> > +				break;
> > +			}
> > +			path[i+1].p_bh = bh;
> 
> Really that should have been "i + 1".  checkpatch misses this.  It seems to
> be missing more stuff that it used to lately.
Done.

Hi Andrew,
Attached is incremental changes to address your comments. 
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
---
 fs/ext4/extents.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Index: linux-2.6.22/fs/ext4/extents.c
===================================================================
--- linux-2.6.22.orig/fs/ext4/extents.c	2007-07-15 23:25:38.000000000 -0700
+++ linux-2.6.22/fs/ext4/extents.c	2007-07-15 23:44:03.000000000 -0700
@@ -239,7 +239,7 @@ static int ext4_ext_space_root_idx(struc
 	return size;
 }
 
-static inline int
+static int
 ext4_ext_max_entries(struct inode *inode, int depth)
 {
 	int max;
@@ -263,7 +263,7 @@ static int __ext4_ext_check_header(const
 					struct ext4_extent_header *eh,
 					int depth)
 {
-	const char *error_msg = NULL;
+	const char *error_msg;
 	int max = 0;
 
 	if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
@@ -498,7 +498,7 @@ ext4_ext_find_extent(struct inode *inode
 	short int depth, i, ppos = 0, alloc = 0;
 
 	eh = ext_inode_hdr(inode);
-	i = depth = ext_depth(inode);
+	depth = ext_depth(inode);
 	if (ext4_ext_check_header(inode, eh, depth))
 		return ERR_PTR(-EIO);
 
@@ -513,6 +513,7 @@ ext4_ext_find_extent(struct inode *inode
 	}
 	path[0].p_hdr = eh;
 
+	i = depth;
 	/* walk through the tree */
 	while (i) {
 		ext_debug("depth %d: num %d, max %d\n",
@@ -1973,13 +1974,16 @@ int ext4_ext_remove_space(struct inode *
 				err = -EIO;
 				break;
 			}
-			BUG_ON(i + 1 > depth);
+			if (WARN_ON(i + 1 > depth)) {
+				err = -EIO;
+				break;
+			}
 			if (ext4_ext_check_header(inode, ext_block_hdr(bh),
 							depth - i - 1)) {
 				err = -EIO;
 				break;
 			}
-			path[i+1].p_bh = bh;
+			path[i + 1].p_bh = bh;
 
 			/* save actual number of indexes since this
 			 * number is changed at the next iteration */