From: Michael Bommarito <michael.bommarito@gmail.com> stable inclusion from stable-v5.10.270 commit 848b80ca6b410f350d08b8ac19a00ef88223f2ea category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/18970 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 68d541754d6cd3bb98d1fd8314f57e5eb533557d upstream. __build_xattrs() decodes the MDS-supplied xattr blob one attribute at a time. For each attribute it reads a 32-bit name length, advances past the name bytes, reads a 32-bit value length, records the value pointer, and advances past the value bytes. The two length fields are read with ceph_decode_32_safe(), but the value bytes themselves are advanced over with a bare "p += len" and no ceph_decode_need() check that "len" bytes remain in the blob. For every attribute except the last, the next iteration's ceph_decode_32_safe() on the following name length implicitly verifies that the previous value did not run past the blob end. The final attribute has no successor, so its decoded value length is never checked against the blob bounds. A malicious or compromised metadata server can set the last attribute's value length larger than the bytes actually present in the blob. The blob is a dedicated kvmalloc() allocation sized to the wire length (ceph_buffer_new() in ceph_fill_inode()). __set_xattr() records the oversized length in xattr->val_len verbatim, and a later getxattr(2) runs memcpy(value, xattr->val, xattr->val_len) into a user-supplied buffer, copying bytes past the end of the allocation back to user space. Impact: a malicious metadata server discloses adjacent kernel heap bytes to a local user via getxattr(2) on a CephFS file. Add the missing ceph_decode_need() so an out-of-bounds value length on the final attribute fails the decode and returns -EIO instead of being stored. Cc: stable@vger.kernel.org Fixes: 355da1eb7a1f ("ceph: inode operations") Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com> Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Pu Lehui <pulehui@huawei.com> --- fs/ceph/xattr.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c index d1fd81b1b541..80f39d46f12d 100644 --- a/fs/ceph/xattr.c +++ b/fs/ceph/xattr.c @@ -715,6 +715,7 @@ static int __build_xattrs(struct inode *inode) name = p; p += len; ceph_decode_32_safe(&p, end, len, bad); + ceph_decode_need(&p, end, len, bad); val = p; p += len; -- 2.34.1