Description

In the Linux kernel, the following vulnerability has been resolved: orangefs: fix xattr related buffer overflow... Willy Tarreau <w@1wt.eu> forwarded me a message from Disclosure <disclosure@aisle.com> with the following warning: > The helper `xattr_key()` uses the pointer variable in the loop condition > rather than dereferencing it. As `key` is incremented, it remains non-NULL > (until it runs into unmapped memory), so the loop does not terminate on > valid C strings and will walk memory indefinitely, consuming CPU or hanging > the thread. I easily reproduced this with setfattr and getfattr, causing a kernel oops, hung user processes and corrupted orangefs files. Disclosure sent along a diff (not a patch) with a suggested fix, which I based this patch on. After xattr_key started working right, xfstest generic/069 exposed an xattr related memory leak that lead to OOM. xattr_key returns a hashed key. When adding xattrs to the orangefs xattr cache, orangefs used hash_add, a kernel hashing macro. hash_add also hashes the key using hash_log which resulted in additions to the xattr cache going to the wrong hash bucket. generic/069 tortures a single file and orangefs does a getattr for the xattr "security.capability" every time. Orangefs negative caches on xattrs which includes a kmalloc. Since adds to the xattr cache were going to the wrong bucket, every getattr for "security.capability" resulted in another kmalloc, none of which were ever freed. I changed the two uses of hash_add to hlist_add_head instead and the memory leak ceased and generic/069 quit throwing furniture.

References 8

• git.kernel.org https://git.kernel.org/stable/c/025e880759c279ec64d0f754fe65bf45961da864
• git.kernel.org https://git.kernel.org/stable/c/15afebb9597449c444801d1ff0b8d8b311f950ab
• git.kernel.org https://git.kernel.org/stable/c/9127d1e90c90e5960c8bc72a4ce2c209691a7021
• git.kernel.org https://git.kernel.org/stable/c/bc812574de633cf9a9ad6974490e45f6a4bb5126
• git.kernel.org https://git.kernel.org/stable/c/c2ca015ac109fd743fdde27933d59dc5ad46658e
• git.kernel.org https://git.kernel.org/stable/c/c6564ff6b53c9a8dc786b6f1c51ae7688273f931
• git.kernel.org https://git.kernel.org/stable/c/e09a096104fc65859422817fb2211f35855983fe
• git.kernel.org https://git.kernel.org/stable/c/ef892d2bf4f3fa2c8de1677dd307e678bdd3d865

Remediation