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ext4: add corruption check in ext4_xattr_set_entry()

PATCH New Daniel Rosenberg 1 participant 1 message Oct 16, 2018

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Stable branch ext4 file system
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Daniel Rosenberg

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PATCH v2 1/1 ext4: add corruption check in ext4_xattr_set_entry()

From: Theodore Ts'o <[email protected]>

commit 5369a762c882c0b6e9599e4ebbb3a9ba9eee7e2d upstream.

In theory this should have been caught earlier when the xattr list was verified, but in case it got missed, it's simple enough to add check to make sure we don't overrun the xattr buffer.

This addresses CVE-2018-10879.

https://bugzilla.kernel.org/show_bug.cgi?id=200001

Signed-off-by Theodore Ts'o <[email protected]>
Reviewed-by Andreas Dilger <[email protected]>

[bwh: Backported to 3.16:
- Add inode parameter to ext4_xattr_set_entry() and update callers
- Adjust context]

Signed-off-by Ben Hutchings <[email protected]>
[adjusted for 4.4 context]
Signed-off-by Daniel Rosenberg <[email protected]>
---
 fs/ext4/xattr.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)
fs/ext4/xattr.c +14 -8
index d0aaf338fa9fa..d6bae37489af0 100644
@@ -638,14 +638,20 @@ static size_t ext4_xattr_free_space(struct ext4_xattr_entry *last,
 }
 
 static int
-ext4_xattr_set_entry(struct ext4_xattr_info *i, struct ext4_xattr_search *s)
+ext4_xattr_set_entry(struct ext4_xattr_info *i, struct ext4_xattr_search *s,
+		     struct inode *inode)
 {
-	struct ext4_xattr_entry *last;
+	struct ext4_xattr_entry *last, *next;
 	size_t free, min_offs = s->end - s->base, name_len = strlen(i->name);
 
 	/* Compute min_offs and last. */
 	last = s->first;
-	for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
+	for (; !IS_LAST_ENTRY(last); last = next) {
+		next = EXT4_XATTR_NEXT(last);
+		if ((void *)next >= s->end) {
+			EXT4_ERROR_INODE(inode, "corrupted xattr entries");
+			return -EFSCORRUPTED;
+		}
 		if (!last->e_value_block && last->e_value_size) {
 			size_t offs = le16_to_cpu(last->e_value_offs);
 			if (offs < min_offs)

@@ -825,7 +831,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 				ce = NULL;
 			}
 			ea_bdebug(bs->bh, "modifying in-place");
-			error = ext4_xattr_set_entry(i, s);
+			error = ext4_xattr_set_entry(i, s, inode);
 			if (!error) {
 				if (!IS_LAST_ENTRY(s->first))
 					ext4_xattr_rehash(header(s->base),

@@ -875,7 +881,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 		s->end = s->base + sb->s_blocksize;
 	}
 
-	error = ext4_xattr_set_entry(i, s);
+	error = ext4_xattr_set_entry(i, s, inode);
 	if (error == -EFSCORRUPTED)
 		goto bad_block;
 	if (error)

@@ -1037,7 +1043,7 @@ int ext4_xattr_ibody_inline_set(handle_t *handle, struct inode *inode,
 
 	if (EXT4_I(inode)->i_extra_isize == 0)
 		return -ENOSPC;
-	error = ext4_xattr_set_entry(i, s);
+	error = ext4_xattr_set_entry(i, s, inode);
 	if (error) {
 		if (error == -ENOSPC &&
 		    ext4_has_inline_data(inode)) {

@@ -1049,7 +1055,7 @@ int ext4_xattr_ibody_inline_set(handle_t *handle, struct inode *inode,
 			error = ext4_xattr_ibody_find(inode, i, is);
 			if (error)
 				return error;
-			error = ext4_xattr_set_entry(i, s);
+			error = ext4_xattr_set_entry(i, s, inode);
 		}
 		if (error)
 			return error;

@@ -1075,7 +1081,7 @@ static int ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
 
 	if (EXT4_I(inode)->i_extra_isize == 0)
 		return -ENOSPC;
-	error = ext4_xattr_set_entry(i, s);
+	error = ext4_xattr_set_entry(i, s, inode);
 	if (error)
 		return error;
 	header = IHDR(inode, ext4_raw_inode(&is->iloc));
Signature · 1 line
2.19.1.331.ge82ca0e54c-goog