CVE-2024-44959

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

tracefs: Use generic inode RCU for synchronizing freeing

With structure layout randomization enabled for struct inode we need to avoid overlapping any of the RCU-used / initialized-only-once members, e.g. i_lru or i_sb_list to not corrupt related list traversals when making use of the rcu_head.

For an unlucky structure layout of struct inode we may end up with the following splat when running the ftrace selftests:

[<…>] list_del corruption, ffff888103ee2cb0->next (tracefs_inode_cache+0x0/0x4e0 [slab object]) is NULL (prev is tracefs_inode_cache+0x78/0x4e0 [slab object]) [<…>] ————[ cut here ]———— [<…>] kernel BUG at lib/list_debug.c:54! [<…>] invalid opcode: 0000 [#1] PREEMPT SMP KASAN [<…>] CPU: 3 PID: 2550 Comm: mount Tainted: G N 6.8.12-grsec+ #122 ed2f536ca62f28b087b90e3cc906a8d25b3ddc65 [<…>] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [<…>] RIP: 0010:[] __list_del_entry_valid_or_report+0x138/0x3e0 [<…>] Code: 48 b8 99 fb 65 f2 ff ff ff ff e9 03 5c d9 fc cc 48 b8 99 fb 65 f2 ff ff ff ff e9 33 5a d9 fc cc 48 b8 99 fb 65 f2 ff ff ff ff <0f> 0b 4c 89 e9 48 89 ea 48 89 ee 48 c7 c7 60 8f dd 89 31 c0 e8 2f [<…>] RSP: 0018:fffffe80416afaf0 EFLAGS: 00010283 [<…>] RAX: 0000000000000098 RBX: ffff888103ee2cb0 RCX: 0000000000000000 [<…>] RDX: ffffffff84655fe8 RSI: ffffffff89dd8b60 RDI: 0000000000000001 [<…>] RBP: ffff888103ee2cb0 R08: 0000000000000001 R09: fffffbd0082d5f25 [<…>] R10: fffffe80416af92f R11: 0000000000000001 R12: fdf99c16731d9b6d [<…>] R13: 0000000000000000 R14: ffff88819ad4b8b8 R15: 0000000000000000 [<…>] RBX: tracefs_inode_cache+0x0/0x4e0 [slab object] [<…>] RDX: __list_del_entry_valid_or_report+0x108/0x3e0 [<…>] RSI: func.47+0x4340/0x4400 [<…>] RBP: tracefs_inode_cache+0x0/0x4e0 [slab object] [<…>] RSP: process kstack fffffe80416afaf0+0x7af0/0x8000 [mount 2550 2550] [<…>] R09: kasan shadow of process kstack fffffe80416af928+0x7928/0x8000 [mount 2550 2550] [<…>] R10: process kstack fffffe80416af92f+0x792f/0x8000 [mount 2550 2550] [<…>] R14: tracefs_inode_cache+0x78/0x4e0 [slab object] [<…>] FS: 00006dcb380c1840(0000) GS:ffff8881e0600000(0000) knlGS:0000000000000000 [<…>] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [<…>] CR2: 000076ab72b30e84 CR3: 000000000b088004 CR4: 0000000000360ef0 shadow CR4: 0000000000360ef0 [<…>] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [<…>] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [<…>] ASID: 0003 [<…>] Stack: [<…>] ffffffff818a2315 00000000f5c856ee ffffffff896f1840 ffff888103ee2cb0 [<…>] ffff88812b6b9750 0000000079d714b6 fffffbfff1e9280b ffffffff8f49405f [<…>] 0000000000000001 0000000000000000 ffff888104457280 ffffffff8248b392 [<…>] Call Trace: [<…>] [<…>] [] ? lock_release+0x175/0x380 fffffe80416afaf0 [<…>] [] list_lru_del+0x152/0x740 fffffe80416afb48 [<…>] [] list_lru_del_obj+0x113/0x280 fffffe80416afb88 [<…>] [] ? _atomic_dec_and_lock+0x119/0x200 fffffe80416afb90 [<…>] [] iput_final+0x1c4/0x9a0 fffffe80416afbb8 [<…>] [] dentry_unlink_inode+0x44b/0xaa0 fffffe80416afbf8 [<…>] [] __dentry_kill+0x23c/0xf00 fffffe80416afc40 [<…>] [] ? __this_cpu_preempt_check+0x1f/0xa0 fffffe80416afc48 [<…>] [] ? shrink_dentry_list+0x1c5/0x760 fffffe80416afc70 [<…>] [] ? shrink_dentry_list+0x51/0x760 fffffe80416afc78 [<…>] [] shrink_dentry_list+0x288/0x760 fffffe80416afc80 [<…>] [] shrink_dcache_sb+0x155/0x420 fffffe80416afcc8 [<…>] [] ? debug_smp_processor_id+0x23/0xa0 fffffe80416afce0 [<…>] [] ? do_one_tre —truncated—

Affected Software

References

• https://git.kernel.org/stable/c/061da60716ce0cde99f62f31937b81e1c03acef6
• https://git.kernel.org/stable/c/0b6743bd60a56a701070b89fb80c327a44b7b3e2
• https://git.kernel.org/stable/c/726f4c241e17be75a9cf6870d80cd7479dc89e8f