From 13dd743a0a7a8c5054cd652541789eab89fc3307 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" Date: Wed, 6 Jul 2022 10:50:40 -0400 Subject: [PATCH] net: sock: tracing: Fix sock_exceed_buf_limit not to dereference stale pointer commit e06b6af08f95abc94b583c466fdb0010242ab03b upstream. The trace event sock_exceed_buf_limit saves the prot->sysctl_mem pointer and then dereferences it in the TP_printk() portion. This is unsafe as the TP_printk() portion is executed at the time the buffer is read. That is, it can be seconds, minutes, days, months, even years later. If the proto is freed, then this dereference will can also lead to a kernel crash. Instead, save the sysctl_mem array into the ring buffer and have the TP_printk() reference that instead. This is the proper and safe way to read pointers in trace events. Link: https://lore.kernel.org/all/20220706052130.16368-12-kuniyu@amazon.com/ Cc: stable@vger.kernel.org Fixes: 64c86253719f3 ("core: add tracepoints for queueing skb to rcvbuf") Signed-off-by: Steven Rostedt (Google) Acked-by: Kuniyuki Iwashima Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/trace/events/sock.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/include/trace/events/sock.h b/include/trace/events/sock.h index 51fe9f6719eb1..ad11938c09725 100644 --- a/include/trace/events/sock.h +++ b/include/trace/events/sock.h @@ -97,7 +97,7 @@ TRACE_EVENT(sock_exceed_buf_limit, TP_STRUCT__entry( __array(char, name, 32) - __field(long *, sysctl_mem) + __array(long, sysctl_mem, 3) __field(long, allocated) __field(int, sysctl_rmem) __field(int, rmem_alloc) @@ -109,7 +109,9 @@ TRACE_EVENT(sock_exceed_buf_limit, TP_fast_assign( strncpy(__entry->name, prot->name, 32); - __entry->sysctl_mem = prot->sysctl_mem; + __entry->sysctl_mem[0] = READ_ONCE(prot->sysctl_mem[0]); + __entry->sysctl_mem[1] = READ_ONCE(prot->sysctl_mem[1]); + __entry->sysctl_mem[2] = READ_ONCE(prot->sysctl_mem[2]); __entry->allocated = allocated; __entry->sysctl_rmem = sk_get_rmem0(sk, prot); __entry->rmem_alloc = atomic_read(&sk->sk_rmem_alloc); -- 2.39.5