[PATCH v2] ftrace: Fix use-after-free for dynamic ftrace_ops
From: Li Huafei
Date: Wed Nov 02 2022 - 23:13:59 EST
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
[...]
Fixes: edb096e00724f ("ftrace: Fix memleak when unregistering dynamic ops when tracing disabled")
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Li Huafei <lihuafei1@xxxxxxxxxx>
---
v1: https://lore.kernel.org/lkml/20221101064146.69551-1-lihuafei1@xxxxxxxxxx/
Changlog in v1 -> v2:
- Cc the stable list as suggested by Masami. I did not add Masami's
Review-by due to some differences from v1. If the new changes are
still okay, please let me know. Thanks to Masami!
- Add Fixes tag as suggested by Steve.
- Remove the 'ftrace_enabled' check.
kernel/trace/ftrace.c | 16 +++-------------
1 file changed, 3 insertions(+), 13 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index fbf2543111c0..7dc023641bf1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3028,18 +3028,8 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
command |= FTRACE_UPDATE_TRACE_FUNC;
}
- 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 (ops->flags & FTRACE_OPS_FL_DYNAMIC)
- goto free_ops;
-
- return 0;
- }
+ if (!command || !ftrace_enabled)
+ goto out;
/*
* If the ops uses a trampoline, then it needs to be
@@ -3076,6 +3066,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
removed_ops = NULL;
ops->flags &= ~FTRACE_OPS_FL_REMOVING;
+out:
/*
* Dynamic ops may be freed, we must make sure that all
* callers are done before leaving this function.
@@ -3103,7 +3094,6 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command)
if (IS_ENABLED(CONFIG_PREEMPTION))
synchronize_rcu_tasks();
- free_ops:
ftrace_trampoline_free(ops);
}
--
2.17.1