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:[<ffffffff84656018>] __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:
[<…>] <TASK>
[<…>] [<ffffffff818a2315>] ? lock_release+0x175/0x380 fffffe80416afaf0
[<…>] [<ffffffff8248b392>] list_lru_del+0x152/0x740 fffffe80416afb48
[<…>] [<ffffffff8248ba93>] list_lru_del_obj+0x113/0x280 fffffe80416afb88
[<…>] [<ffffffff8940fd19>] ? _atomic_dec_and_lock+0x119/0x200 fffffe80416afb90
[<…>] [<ffffffff8295b244>] iput_final+0x1c4/0x9a0 fffffe80416afbb8
[<…>] [<ffffffff8293a52b>] dentry_unlink_inode+0x44b/0xaa0 fffffe80416afbf8
[<…>] [<ffffffff8293fefc>] __dentry_kill+0x23c/0xf00 fffffe80416afc40
[<…>] [<ffffffff8953a85f>] ? __this_cpu_preempt_check+0x1f/0xa0 fffffe80416afc48
[<…>] [<ffffffff82949ce5>] ? shrink_dentry_list+0x1c5/0x760 fffffe80416afc70
[<…>] [<ffffffff82949b71>] ? shrink_dentry_list+0x51/0x760 fffffe80416afc78
[<…>] [<ffffffff82949da8>] shrink_dentry_list+0x288/0x760 fffffe80416afc80
[<…>] [<ffffffff8294ae75>] shrink_dcache_sb+0x155/0x420 fffffe80416afcc8
[<…>] [<ffffffff8953a7c3>] ? debug_smp_processor_id+0x23/0xa0 fffffe80416afce0
[<…>] [<ffffffff8294ad20>] ? do_one_tre
—truncated—