--- /dev/null
+From 3e08a9f9760f4a70d633c328a76408e62d6f80a3 Mon Sep 17 00:00:00 2001
+From: Liangyan <liangyan.peng@linux.alibaba.com>
+Date: Mon, 7 Jun 2021 20:57:34 +0800
+Subject: tracing: Correct the length check which causes memory corruption
+
+From: Liangyan <liangyan.peng@linux.alibaba.com>
+
+commit 3e08a9f9760f4a70d633c328a76408e62d6f80a3 upstream.
+
+We've suffered from severe kernel crashes due to memory corruption on
+our production environment, like,
+
+Call Trace:
+[1640542.554277] general protection fault: 0000 [#1] SMP PTI
+[1640542.554856] CPU: 17 PID: 26996 Comm: python Kdump: loaded Tainted:G
+[1640542.556629] RIP: 0010:kmem_cache_alloc+0x90/0x190
+[1640542.559074] RSP: 0018:ffffb16faa597df8 EFLAGS: 00010286
+[1640542.559587] RAX: 0000000000000000 RBX: 0000000000400200 RCX:
+0000000006e931bf
+[1640542.560323] RDX: 0000000006e931be RSI: 0000000000400200 RDI:
+ffff9a45ff004300
+[1640542.560996] RBP: 0000000000400200 R08: 0000000000023420 R09:
+0000000000000000
+[1640542.561670] R10: 0000000000000000 R11: 0000000000000000 R12:
+ffffffff9a20608d
+[1640542.562366] R13: ffff9a45ff004300 R14: ffff9a45ff004300 R15:
+696c662f65636976
+[1640542.563128] FS: 00007f45d7c6f740(0000) GS:ffff9a45ff840000(0000)
+knlGS:0000000000000000
+[1640542.563937] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
+[1640542.564557] CR2: 00007f45d71311a0 CR3: 000000189d63e004 CR4:
+00000000003606e0
+[1640542.565279] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
+0000000000000000
+[1640542.566069] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
+0000000000000400
+[1640542.566742] Call Trace:
+[1640542.567009] anon_vma_clone+0x5d/0x170
+[1640542.567417] __split_vma+0x91/0x1a0
+[1640542.567777] do_munmap+0x2c6/0x320
+[1640542.568128] vm_munmap+0x54/0x70
+[1640542.569990] __x64_sys_munmap+0x22/0x30
+[1640542.572005] do_syscall_64+0x5b/0x1b0
+[1640542.573724] entry_SYSCALL_64_after_hwframe+0x44/0xa9
+[1640542.575642] RIP: 0033:0x7f45d6e61e27
+
+James Wang has reproduced it stably on the latest 4.19 LTS.
+After some debugging, we finally proved that it's due to ftrace
+buffer out-of-bound access using a debug tool as follows:
+[ 86.775200] BUG: Out-of-bounds write at addr 0xffff88aefe8b7000
+[ 86.780806] no_context+0xdf/0x3c0
+[ 86.784327] __do_page_fault+0x252/0x470
+[ 86.788367] do_page_fault+0x32/0x140
+[ 86.792145] page_fault+0x1e/0x30
+[ 86.795576] strncpy_from_unsafe+0x66/0xb0
+[ 86.799789] fetch_memory_string+0x25/0x40
+[ 86.804002] fetch_deref_string+0x51/0x60
+[ 86.808134] kprobe_trace_func+0x32d/0x3a0
+[ 86.812347] kprobe_dispatcher+0x45/0x50
+[ 86.816385] kprobe_ftrace_handler+0x90/0xf0
+[ 86.820779] ftrace_ops_assist_func+0xa1/0x140
+[ 86.825340] 0xffffffffc00750bf
+[ 86.828603] do_sys_open+0x5/0x1f0
+[ 86.832124] do_syscall_64+0x5b/0x1b0
+[ 86.835900] entry_SYSCALL_64_after_hwframe+0x44/0xa9
+
+commit b220c049d519 ("tracing: Check length before giving out
+the filter buffer") adds length check to protect trace data
+overflow introduced in 0fc1b09ff1ff, seems that this fix can't prevent
+overflow entirely, the length check should also take the sizeof
+entry->array[0] into account, since this array[0] is filled the
+length of trace data and occupy addtional space and risk overflow.
+
+Link: https://lkml.kernel.org/r/20210607125734.1770447-1-liangyan.peng@linux.alibaba.com
+
+Cc: stable@vger.kernel.org
+Cc: Ingo Molnar <mingo@redhat.com>
+Cc: Xunlei Pang <xlpang@linux.alibaba.com>
+Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Fixes: b220c049d519 ("tracing: Check length before giving out the filter buffer")
+Reviewed-by: Xunlei Pang <xlpang@linux.alibaba.com>
+Reviewed-by: yinbinbin <yinbinbin@alibabacloud.com>
+Reviewed-by: Wetp Zhang <wetp.zy@linux.alibaba.com>
+Tested-by: James Wang <jnwang@linux.alibaba.com>
+Signed-off-by: Liangyan <liangyan.peng@linux.alibaba.com>
+Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ kernel/trace/trace.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/kernel/trace/trace.c
++++ b/kernel/trace/trace.c
+@@ -2734,7 +2734,7 @@ trace_event_buffer_lock_reserve(struct t
+ (entry = this_cpu_read(trace_buffered_event))) {
+ /* Try to use the per cpu buffer first */
+ val = this_cpu_inc_return(trace_buffered_event_cnt);
+- if ((len < (PAGE_SIZE - sizeof(*entry))) && val == 1) {
++ if ((len < (PAGE_SIZE - sizeof(*entry) - sizeof(entry->array[0]))) && val == 1) {
+ trace_event_setup(entry, type, flags, pc);
+ entry->array[0] = len;
+ return entry;