| From 0dcd7876029b58770f769cbb7b484e88e4a305e5 Mon Sep 17 00:00:00 2001 |
| From: Greg Hackmann <ghackmann@google.com> |
| Date: Wed, 7 Mar 2018 14:42:53 -0800 |
| Subject: net: xfrm: use preempt-safe this_cpu_read() in ipcomp_alloc_tfms() |
| |
| From: Greg Hackmann <ghackmann@google.com> |
| |
| commit 0dcd7876029b58770f769cbb7b484e88e4a305e5 upstream. |
| |
| f7c83bcbfaf5 ("net: xfrm: use __this_cpu_read per-cpu helper") added a |
| __this_cpu_read() call inside ipcomp_alloc_tfms(). |
| |
| At the time, __this_cpu_read() required the caller to either not care |
| about races or to handle preemption/interrupt issues. 3.15 tightened |
| the rules around some per-cpu operations, and now __this_cpu_read() |
| should never be used in a preemptible context. On 3.15 and later, we |
| need to use this_cpu_read() instead. |
| |
| syzkaller reported this leading to the following kernel BUG while |
| fuzzing sendmsg: |
| |
| BUG: using __this_cpu_read() in preemptible [00000000] code: repro/3101 |
| caller is ipcomp_init_state+0x185/0x990 |
| CPU: 3 PID: 3101 Comm: repro Not tainted 4.16.0-rc4-00123-g86f84779d8e9 #154 |
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 |
| Call Trace: |
| dump_stack+0xb9/0x115 |
| check_preemption_disabled+0x1cb/0x1f0 |
| ipcomp_init_state+0x185/0x990 |
| ? __xfrm_init_state+0x876/0xc20 |
| ? lock_downgrade+0x5e0/0x5e0 |
| ipcomp4_init_state+0xaa/0x7c0 |
| __xfrm_init_state+0x3eb/0xc20 |
| xfrm_init_state+0x19/0x60 |
| pfkey_add+0x20df/0x36f0 |
| ? pfkey_broadcast+0x3dd/0x600 |
| ? pfkey_sock_destruct+0x340/0x340 |
| ? pfkey_seq_stop+0x80/0x80 |
| ? __skb_clone+0x236/0x750 |
| ? kmem_cache_alloc+0x1f6/0x260 |
| ? pfkey_sock_destruct+0x340/0x340 |
| ? pfkey_process+0x62a/0x6f0 |
| pfkey_process+0x62a/0x6f0 |
| ? pfkey_send_new_mapping+0x11c0/0x11c0 |
| ? mutex_lock_io_nested+0x1390/0x1390 |
| pfkey_sendmsg+0x383/0x750 |
| ? dump_sp+0x430/0x430 |
| sock_sendmsg+0xc0/0x100 |
| ___sys_sendmsg+0x6c8/0x8b0 |
| ? copy_msghdr_from_user+0x3b0/0x3b0 |
| ? pagevec_lru_move_fn+0x144/0x1f0 |
| ? find_held_lock+0x32/0x1c0 |
| ? do_huge_pmd_anonymous_page+0xc43/0x11e0 |
| ? lock_downgrade+0x5e0/0x5e0 |
| ? get_kernel_page+0xb0/0xb0 |
| ? _raw_spin_unlock+0x29/0x40 |
| ? do_huge_pmd_anonymous_page+0x400/0x11e0 |
| ? __handle_mm_fault+0x553/0x2460 |
| ? __fget_light+0x163/0x1f0 |
| ? __sys_sendmsg+0xc7/0x170 |
| __sys_sendmsg+0xc7/0x170 |
| ? SyS_shutdown+0x1a0/0x1a0 |
| ? __do_page_fault+0x5a0/0xca0 |
| ? lock_downgrade+0x5e0/0x5e0 |
| SyS_sendmsg+0x27/0x40 |
| ? __sys_sendmsg+0x170/0x170 |
| do_syscall_64+0x19f/0x640 |
| entry_SYSCALL_64_after_hwframe+0x42/0xb7 |
| RIP: 0033:0x7f0ee73dfb79 |
| RSP: 002b:00007ffe14fc15a8 EFLAGS: 00000207 ORIG_RAX: 000000000000002e |
| RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0ee73dfb79 |
| RDX: 0000000000000000 RSI: 00000000208befc8 RDI: 0000000000000004 |
| RBP: 00007ffe14fc15b0 R08: 00007ffe14fc15c0 R09: 00007ffe14fc15c0 |
| R10: 0000000000000000 R11: 0000000000000207 R12: 0000000000400440 |
| R13: 00007ffe14fc16b0 R14: 0000000000000000 R15: 0000000000000000 |
| |
| Signed-off-by: Greg Hackmann <ghackmann@google.com> |
| Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| net/xfrm/xfrm_ipcomp.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/net/xfrm/xfrm_ipcomp.c |
| +++ b/net/xfrm/xfrm_ipcomp.c |
| @@ -283,7 +283,7 @@ static struct crypto_comp * __percpu *ip |
| struct crypto_comp *tfm; |
| |
| /* This can be any valid CPU ID so we don't need locking. */ |
| - tfm = __this_cpu_read(*pos->tfms); |
| + tfm = this_cpu_read(*pos->tfms); |
| |
| if (!strcmp(crypto_comp_name(tfm), alg_name)) { |
| pos->users++; |