[v2,0/2] ocfs2: add checks in ocfs2_xattr_find_entry() to avoid potential out-of-bound access.

Message

Ferry Meng May 17, 2024, 9:41 a.m. UTC

Hi, all:

This patch series attempts to address a scenario where accessing user-defined
xattrs in a carefully crafted image can lead to out-of-bound access.(To speak
truthfully, I do not think this vehavior would occur under proper usage.)

In my testing environment, I constructed an OCFS2 image, created a file with
several user-defined xattrs(long name attributes, this will cause a "Non-INLINE"
xattr, which requires additional space for storage), and then forcibly modified
the xe_name_offset using a binary editing tool (e.g "hexedit"). Upon remounting
the image and running 'getfattr -d /path/to/file', this patchset was able to 
detect "partial" malicious modification.

In v2, I make these changes:
- (1/2) use xs->end directly, no need to parse a parameter.
- (2/2) define a local var 'name_offset'.

Ferry Meng (2):
  ocfs2: add bounds checking to ocfs2_xattr_find_entry()
  ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()

 fs/ocfs2/xattr.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)