audit: avoid dropping live tree ref on fsnotify rule autoremove

Overview

In the Linux kernel, the following vulnerability has been resolved:

audit: avoid dropping live tree ref on fsnotify rule autoremove

audit_del_rule() is used for both netlink deletion templates and internal fsnotify autoremove. The former passes a parsed template which owns a temporary tree reference; the latter passes the installed entry itself.

The unconditional audit_put_tree() at the end of audit_del_rule() assumes the template case. For mixed AUDIT_DIR plus AUDIT_EXE rules, an fsnotify autoremove event therefore drops the installed rule's live tree reference. Repeating this across rules sharing the same tree can free the tree while another rule still references it, and a later autoremove dereferences the freed pathname while comparing rules.

Move the temporary-tree put to audit_rule_change(), the caller that owns deletion templates. Keep it in the AUDIT_DEL_RULE cleanup so both successful deletion and -ENOENT still release the parser-owned tree.

[PM: dropped unnecessary comment for line length reasons]

Affected

• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < 9cac21f8eb82675ed19fb955b8bbb9dd14cc3d58
• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < b322cc7adcd2e6ec1594d187533a126506ab545c
• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < 695c85dc345a4e0292739f004c261bedef3f27e6
• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < 01b0ec8c397be65ff710777c97017ca1de56ef8e
• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < cf37b61b5420fd4600fe78cf8c24da6e4d9bfe28
• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < 636a99bab36ba27515363d325866c0273ac83b3e
• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < 583cf579b32d99e3fe4e9c8ecc4d852e3708fbec
• Linux >= 34d99af52ad40bd498ba66970579a5bc1fb1a3bc < 783f0f0974c156aca630f4ffff248671082a098d
• Linux 4.3

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.