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>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e3e1978..59a518a 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4527,7 +4527,9 @@ static inline void ext4_iget_extra_inode(struct inode *inode,
 {
        __le32 *magic = (void *)raw_inode +
                        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_find_inline_data_nolock(inode);
        } else

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 1846e91..59c9ec7 100644 (file)
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -231,13 +231,12 @@ static int
 __xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header,
                         void *end, const char *function, unsigned int line)
 {
-       struct ext4_xattr_entry *entry = IFIRST(header);
        int error = -EFSCORRUPTED;
 
-       if (((void *) header >= end) ||
+       if (end - (void *)header < sizeof(*header) + sizeof(u32) ||
            (header->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC)))
                goto errout;
-       error = ext4_xattr_check_names(entry, end, entry);
+       error = ext4_xattr_check_names(IFIRST(header), end, IFIRST(header));
 errout:
        if (error)
                __ext4_error_inode(inode, function, line, 0,