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ext4: don't read out of bounds when checking for in-inode xattrs 

With i_extra_isize equal to or close to the available space, it was
possible for us to read past the end of the inode when trying to detect
or validate in-inode xattrs.  Fix this by checking for the needed extra
space first.

This patch shouldn't have any noticeable effect on
non-corrupted/non-malicious filesystems.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
This commit is contained in:
Eric Biggers 2016-12-01 14:51:58 -05:00 committed by Theodore Ts'o
parent 2dc8d9e19b
commit 290ab23001
2 changed files with 5 additions and 4 deletions
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4
fs/ext4/inode.c
View File

@ -4527,7 +4527,9 @@ static inline void ext4_iget_extra_inode(struct inode *inode,
{ {
__le32 *magic = (void *)raw_inode + __le32 *magic = (void *)raw_inode +
EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize; EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize;
if (*magic == cpu_to_le32(EXT4_XATTR_MAGIC)) { if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize + sizeof(__le32) <=
EXT4_INODE_SIZE(inode->i_sb) &&
*magic == cpu_to_le32(EXT4_XATTR_MAGIC)) {
ext4_set_inode_state(inode, EXT4_STATE_XATTR); ext4_set_inode_state(inode, EXT4_STATE_XATTR);
ext4_find_inline_data_nolock(inode); ext4_find_inline_data_nolock(inode);
} else } else

5
fs/ext4/xattr.c
View File

@ -231,13 +231,12 @@ static int
__xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header, __xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header,
void *end, const char *function, unsigned int line) void *end, const char *function, unsigned int line)
{ {
struct ext4_xattr_entry *entry = IFIRST(header);
int error = -EFSCORRUPTED; int error = -EFSCORRUPTED;
if (((void *) header >= end) || if (end - (void *)header < sizeof(*header) + sizeof(u32) ||
(header->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC))) (header->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC)))
goto errout; goto errout;
error = ext4_xattr_check_names(entry, end, entry); error = ext4_xattr_check_names(IFIRST(header), end, IFIRST(header));
errout: errout:
if (error) if (error)
__ext4_error_inode(inode, function, line, 0, __ext4_error_inode(inode, function, line, 0,