From: Li Huafei lihuafei1@huawei.com
hulk inclusion category: bugfix bugzilla: 50618 CVE: NA
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We got a use-after-free report when doing kernel fuzz tests with KSSAN turned on:
[ 1367.884099] BUG: KASAN: use-after-free in ftrace_ops_list_func+0xf7/0x220 [ 1367.885153] Read of size 8 at addr ffff8884f81a47d0 by tasksyz-executor/99086 [ 1367.886517] CPU: 2 PID: 99086 Comm: syz-executor Kdump: loaded Tainted: G --------- -t -4.18.0-147.5.1.2.h379.kasan.eulerosv2r9.x86_64 #1 [ 1367.886522] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014 [ 1367.886525] Call Trace: [ 1367.886534] dump_stack+0xc2/0x12e [ 1367.886542] ? orc_sort_cmp+0xb0/0xb0 [ 1367.886551] print_address_description+0x70/0x360 [ 1367.886558] ? orc_sort_cmp+0xb0/0xb0 [ 1367.886566] ? perf_trace_buf_alloc+0x190/0x190 [ 1367.886571] kasan_report+0x1b2/0x330 [ 1367.886578] ? ftrace_ops_list_func+0xf7/0x220 [ 1367.886585] ? orc_find+0x560/0x5a0 [ 1367.886597] ? ftrace_ops_list_func+0xf7/0x220 [ 1367.886603] ftrace_ops_list_func+0xf7/0x220 [ 1367.886609] ? __save_stack_trace+0x92/0x100 [ 1367.886616] ftrace_call+0x5/0x34 [ 1367.886623] ? do_syscall_64+0x98/0x2c0 [ 1367.886629] ? do_syscall_64+0x98/0x2c0 [ 1367.886635] ? deref_stack_reg+0xd0/0xd0 [ 1367.886644] ? unwind_get_return_address+0x5/0x50 [ 1367.886651] unwind_get_return_address+0x5/0x50 [ 1367.886656] __save_stack_trace+0x92/0x100 [ 1367.886665] ? do_syscall_64+0x98/0x2c0 [ 1367.886673] save_stack+0x47/0xd0 [ 1367.886680] ? __kasan_slab_free+0x130/0x180 [ 1367.886685] ? kfree+0xa5/0x1e0 [ 1367.886692] ? cgroup_show_path+0x1fd/0x250 [ 1367.886699] ? kernfs_sop_show_path+0xad/0xf0 [ 1367.886705] ? show_mountinfo+0x169/0x4c0 [ 1367.886712] ? seq_read+0x716/0x950 [ 1367.886718] ? __vfs_read+0x55/0xb0 [ 1367.886723] ? vfs_read+0xe7/0x210 [ 1367.886729] ? ksys_pread64+0x95/0xd0 [ 1367.886734] ? objects_show+0x10/0x10 [ 1367.886740] ? ftrace_ops_test+0xba/0x120 [ 1367.886746] ? ftrace_find_tramp_ops_next+0x90/0x90 [ 1367.886753] ? ftrace_find_tramp_ops_next+0x90/0x90 [ 1367.886760] ? ftrace_find_tramp_ops_next+0x90/0x90 [ 1367.886766] ? objects_show+0x10/0x10 [ 1367.886772] ? ftrace_ops_list_func+0x147/0x220 [ 1367.886778] ? __kasan_slab_free+0xac/0x180 [ 1367.886784] ? cgroup_show_path+0x1fd/0x250 [ 1367.886790] ? ftrace_call+0x5/0x34 [ 1367.886796] ? cgroup_show_path+0x1fd/0x250 [ 1367.886802] ? cgroup_show_path+0x1fd/0x250 [ 1367.886811] ? fixup_red_left+0x5/0x30 [ 1367.886817] ? cgroup_show_path+0x1fd/0x250 [ 1367.886824] __kasan_slab_free+0x130/0x180 [ 1367.886831] ? cgroup_show_path+0x1fd/0x250 [ 1367.886835] kfree+0xa5/0x1e0 [ 1367.886842] cgroup_show_path+0x1fd/0x250 [ 1367.886850] ? init_and_link_css+0x370/0x370 [ 1367.886856] kernfs_sop_show_path+0xad/0xf0 [ 1367.886863] show_mountinfo+0x169/0x4c0 [ 1367.886869] ? kernfs_test_super+0x80/0x80 [ 1367.886875] ? show_vfsmnt+0x270/0x270 [ 1367.886880] ? m_next+0x32/0x80 [ 1367.886886] ? show_vfsmnt+0x270/0x270 [ 1367.886891] ? m_show+0x31/0x50 [ 1367.886900] seq_read+0x716/0x950 [ 1367.886911] ? seq_lseek+0x1e0/0x1e0 [ 1367.886916] ? ftrace_call+0x5/0x34 [ 1367.886922] ? ftrace_call+0x5/0x34 [ 1367.886931] ? seq_lseek+0x1e0/0x1e0 [ 1367.886938] __vfs_read+0x55/0xb0 [ 1367.886945] vfs_read+0xe7/0x210 [ 1367.886954] ksys_pread64+0x95/0xd0 [ 1367.886961] do_syscall_64+0x98/0x2c0 [ 1367.886971] entry_SYSCALL_64_after_hwframe+0x65/0xca [ 1367.886976] RIP: 0033:0x46436d [ 1367.886983] Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b4 ff ff ff f7 d8 64 89 01 48 [ 1367.886987] RSP: 002b:00007f83ffff4c28 EFLAGS: 00000246 ORIG_RAX: 0000000000000011 [ 1367.886999] RAX: ffffffffffffffda RBX: 000000000057cfa0 RCX: 000000000046436d [ 1367.887002] RDX: 0000000000001000 RSI: 0000000020000140 RDI: 0000000000000003 [ 1367.887006] RBP: 000000000057cfa0 R08: 0000000000000000 R09: 0000000000000000 [ 1367.887009] R10: 0000000000000000 R11: 0000000000000246 R12: 000000000057cfac [ 1367.887013] R13: 00007f83ffff5700 R14: 00000000004d1e47 R15: 0000000000000fff
[ 1367.887275] Allocated by task 99101: [ 1367.887848] kasan_kmalloc+0xa0/0xd0 [ 1367.887853] kmem_cache_alloc_trace+0xfc/0x220 [ 1367.887860] perf_event_alloc.part.19+0x50/0x14d0 [ 1367.887865] perf_event_alloc+0x67/0x90 [ 1367.887871] __do_sys_perf_event_open+0x20e/0x14c0 [ 1367.887876] do_syscall_64+0x98/0x2c0 [ 1367.887882] entry_SYSCALL_64_after_hwframe+0x65/0xca
[ 1367.888133] Freed by task 99101: [ 1367.888651] __kasan_slab_free+0x130/0x180 [ 1367.888655] kfree+0xa5/0x1e0 [ 1367.888661] perf_event_alloc.part.19+0xca4/0x14d0 [ 1367.888666] perf_event_alloc+0x67/0x90 [ 1367.888672] __do_sys_perf_event_open+0x20e/0x14c0 [ 1367.888677] do_syscall_64+0x98/0x2c0 [ 1367.888683] entry_SYSCALL_64_after_hwframe+0x65/0xca
[ 1367.888935] The buggy address belongs to the object at ffff8884f81a4400 which belongs to the cache kmalloc-2k of size 2048 [ 1367.890854] The buggy address is located 976 bytes inside of 2048-byte region [ffff8884f81a4400, ffff8884f81a4c00) [ 1367.892661] The buggy address belongs to the page: [ 1367.893404] page:ffffea0013e06800 count:1 mapcount:0 mapping:ffff888107c0cf00 index:0x0 compound_mapcount: 0 [ 1367.894915] flags: 0x17ffffc0008100(slab|head) [ 1367.895613] raw: 0017ffffc0008100 ffffea0014bda208 ffffea00140c4208 ffff888107c0cf00 [ 1367.896808] raw: 0000000000000000 00000000000f000f 00000001ffffffff 0000000000000000 [ 1367.898000] page dumped because: kasan: bad access detected
[ 1367.899107] Memory state around the buggy address: [ 1367.899880] ffff8884f81a4680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 1367.900995] ffff8884f81a4700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 1367.902106] >ffff8884f81a4780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 1367.903218]
[ 1367.904122] ffff8884f81a4800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 1367.905234] ffff8884f81a4880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
There is a race between perf_alloc_event() and __ftrace_ops_list_func() on 'event'. When adding a perf event, if the event needs to use the trace framework, it needs to register ftrace_ops with ftrace, which is a structural member of perf event. If perf_alloc_event() fails, it will release the event directly, but if ftrace_ops has been successfully registered, and the corresponding trace point is triggered, then __ftrace_ops_list_func() will still reference the ftrace_ops that perf just registered, but it has been released with the event is freed, so use-after-free happens.
__ftrace_ops_list_func() uses rcu synchronization to access ftrace_ops, so in perf_alloc_event() we call synchronize_rcu() before releasing 'event' to make sure all 'event' references are complete.
Signed-off-by: Yang JiHong yangjihong1@huawei.com Signed-off-by: Li Huafei lihuafei1@huawei.com Reviewed-by: Kuohai Xu xukuohai@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- kernel/events/core.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 42da44e6a5e09..e41d6a5221277 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10251,6 +10251,8 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, put_pid_ns(event->ns); if (event->hw.target) put_task_struct(event->hw.target); + + synchronize_rcu(); kfree(event);
return ERR_PTR(err);