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Message-ID: <0f19ce07-d822-1ca1-3e28-86fb73c348a2@huawei.com>
Date: Tue, 1 Nov 2022 14:52:07 +0800
From: Li Huafei <lihuafei1@...wei.com>
To: <rostedt@...dmis.org>
CC: <mhiramat@...nel.org>, <mark.rutland@....com>,
<linux-kernel@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] ftrace: Fix use-after-free for dynamic ftrace_ops
The subject prefix was messed up, please ignore this patch. I've resent it:
https://lore.kernel.org/lkml/20221101064146.69551-1-lihuafei1@huawei.com/
Thanks!
On 2022/11/1 14:37, Li Huafei wrote:
> KASAN reported a use-after-free with ftrace ops [1]. It was found from
> vmcore that perf had registered two ops with the same content
> successively, both dynamic. After unregistering the second ops, a
> use-after-free occurred.
>
> In ftrace_shutdown(), when the second ops is unregistered, the
> FTRACE_UPDATE_CALLS command is not set because there is another enabled
> ops with the same content. Also, both ops are dynamic and the ftrace
> callback function is ftrace_ops_list_func, so the
> FTRACE_UPDATE_TRACE_FUNC command will not be set. Eventually the value
> of 'command' will be 0 and ftrace_shutdown() will skip the rcu
> synchronization.
>
> However, ftrace may be activated. When the ops is released, another CPU
> may be accessing the ops. Add the missing synchronization to fix this
> problem.
>
> [1]
> BUG: KASAN: use-after-free in __ftrace_ops_list_func kernel/trace/ftrace.c:7020 [inline]
> BUG: KASAN: use-after-free in ftrace_ops_list_func+0x2b0/0x31c kernel/trace/ftrace.c:7049
> Read of size 8 at addr ffff56551965bbc8 by task syz-executor.2/14468
>
> CPU: 1 PID: 14468 Comm: syz-executor.2 Not tainted 5.10.0 #7
> Hardware name: linux,dummy-virt (DT)
> Call trace:
> dump_backtrace+0x0/0x40c arch/arm64/kernel/stacktrace.c:132
> show_stack+0x30/0x40 arch/arm64/kernel/stacktrace.c:196
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x1b4/0x248 lib/dump_stack.c:118
> print_address_description.constprop.0+0x28/0x48c mm/kasan/report.c:387
> __kasan_report mm/kasan/report.c:547 [inline]
> kasan_report+0x118/0x210 mm/kasan/report.c:564
> check_memory_region_inline mm/kasan/generic.c:187 [inline]
> __asan_load8+0x98/0xc0 mm/kasan/generic.c:253
> __ftrace_ops_list_func kernel/trace/ftrace.c:7020 [inline]
> ftrace_ops_list_func+0x2b0/0x31c kernel/trace/ftrace.c:7049
> ftrace_graph_call+0x0/0x4
> __might_sleep+0x8/0x100 include/linux/perf_event.h:1170
> __might_fault mm/memory.c:5183 [inline]
> __might_fault+0x58/0x70 mm/memory.c:5171
> do_strncpy_from_user lib/strncpy_from_user.c:41 [inline]
> strncpy_from_user+0x1f4/0x4b0 lib/strncpy_from_user.c:139
> getname_flags+0xb0/0x31c fs/namei.c:149
> getname+0x2c/0x40 fs/namei.c:209
> [...]
>
> Allocated by task 14445:
> kasan_save_stack+0x24/0x50 mm/kasan/common.c:48
> kasan_set_track mm/kasan/common.c:56 [inline]
> __kasan_kmalloc mm/kasan/common.c:479 [inline]
> __kasan_kmalloc.constprop.0+0x110/0x13c mm/kasan/common.c:449
> kasan_kmalloc+0xc/0x14 mm/kasan/common.c:493
> kmem_cache_alloc_trace+0x440/0x924 mm/slub.c:2950
> kmalloc include/linux/slab.h:563 [inline]
> kzalloc include/linux/slab.h:675 [inline]
> perf_event_alloc.part.0+0xb4/0x1350 kernel/events/core.c:11230
> perf_event_alloc kernel/events/core.c:11733 [inline]
> __do_sys_perf_event_open kernel/events/core.c:11831 [inline]
> __se_sys_perf_event_open+0x550/0x15f4 kernel/events/core.c:11723
> __arm64_sys_perf_event_open+0x6c/0x80 kernel/events/core.c:11723
> [...]
>
> Freed by task 14445:
> kasan_save_stack+0x24/0x50 mm/kasan/common.c:48
> kasan_set_track+0x24/0x34 mm/kasan/common.c:56
> kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:358
> __kasan_slab_free.part.0+0x11c/0x1b0 mm/kasan/common.c:437
> __kasan_slab_free mm/kasan/common.c:445 [inline]
> kasan_slab_free+0x2c/0x40 mm/kasan/common.c:446
> slab_free_hook mm/slub.c:1569 [inline]
> slab_free_freelist_hook mm/slub.c:1608 [inline]
> slab_free mm/slub.c:3179 [inline]
> kfree+0x12c/0xc10 mm/slub.c:4176
> perf_event_alloc.part.0+0xa0c/0x1350 kernel/events/core.c:11434
> perf_event_alloc kernel/events/core.c:11733 [inline]
> __do_sys_perf_event_open kernel/events/core.c:11831 [inline]
> __se_sys_perf_event_open+0x550/0x15f4 kernel/events/core.c:11723
> [...]
>
> Signed-off-by: Li Huafei <lihuafei1@...wei.com>
> ---
> kernel/trace/ftrace.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index fbf2543111c0..4219cc2a04a6 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3030,13 +3030,16 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
>
> if (!command || !ftrace_enabled) {
> /*
> - * If these are dynamic or per_cpu ops, they still
> - * need their data freed. Since, function tracing is
> - * not currently active, we can just free them
> - * without synchronizing all CPUs.
> + * If these are dynamic, they still need their data freed. If
> + * function tracing is currently active, we neet to synchronize
> + * all CPUs before we can release them.
> */
> - if (ops->flags & FTRACE_OPS_FL_DYNAMIC)
> + if (ops->flags & FTRACE_OPS_FL_DYNAMIC) {
> + if (ftrace_enabled)
> + goto sync_rcu;
> +
> goto free_ops;
> + }
>
> return 0;
> }
> @@ -3083,6 +3086,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
> * ops.
> */
> if (ops->flags & FTRACE_OPS_FL_DYNAMIC) {
> + sync_rcu:
> /*
> * We need to do a hard force of sched synchronization.
> * This is because we use preempt_disable() to do RCU, but
>
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