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Date: Fri, 3 Mar 2023 18:02:17 +0800
From: "liuwenyu (D)" <liuwenyu7@...wei.com>
To: <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
<mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
<jolsa@...nel.org>, <namhyung@...nel.org>, <irogers@...gle.com>,
<brauner@...nel.org>, <adrian.hunter@...el.com>,
<linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <linfeilong@...wei.com>, "hewenliang (C)" <hewenliang4@...wei.com>,
<yeyunfeng@...wei.com>, Wenyu Liu <liuwenyu7@...wei.com>
Subject: [PATCH] perf top: Fix rare segfault in thread__comm_len()
In thread__comm_len(),strlen() is called outside of the
thread->comm_lock critical section,which may cause a UAF
problems if comm__free() is called by the process_thread
concurrently.
backtrace of the core file is as follows:
(gdb) bt
#0 __strlen_evex () at ../sysdeps/x86_64/multiarch/strlen-evex.S:77
#1 0x000055ad15d31de5 in thread__comm_len (thread=0x7f627d20e300)
at util/thread.c:320
#2 0x000055ad15d4fade in hists__calc_col_len (h=0x7f627d295940,
hists=0x55ad1772bfe0)
at util/hist.c:103
#3 hists__calc_col_len (hists=0x55ad1772bfe0, h=0x7f627d295940) at
util/hist.c:79
#4 0x000055ad15d52c8c in output_resort
(hists=hists@...ry=0x55ad1772bfe0, prog=0x0,
use_callchain=false, cb=cb@...ry=0x0, cb_arg=0x0) at
util/hist.c:1926
#5 0x000055ad15d530a4 in evsel__output_resort_cb
(evsel=evsel@...ry=0x55ad1772bde0,
prog=prog@...ry=0x0, cb=cb@...ry=0x0, cb_arg=cb_arg@...ry=0x0)
at util/hist.c:1945
#6 0x000055ad15d53110 in evsel__output_resort
(evsel=evsel@...ry=0x55ad1772bde0,
prog=prog@...ry=0x0) at util/hist.c:1950
#7 0x000055ad15c6ae9a in perf_top__resort_hists
(t=t@...ry=0x7ffcd9cbf4f0) at builtin-top.c:311
#8 0x000055ad15c6cc6d in perf_top__print_sym_table
(top=0x7ffcd9cbf4f0) at builtin-top.c:346
#9 display_thread (arg=0x7ffcd9cbf4f0) at builtin-top.c:700
#10 0x00007f6282fab4fa in start_thread (arg=<optimized out>) at
pthread_create.c:443
#11 0x00007f628302e200 in clone3 () at
../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
The reason is that strlen() get a pointer to a memory that has been freed.
The string pointer is stored in the structure comm_str, which corresponds
to a rb_tree node,when the node is erased, the memory of the string is
also freed.
In thread__comm_len(),it gets the pointer within the thread->comm_lock
critical section,
but passed to strlen() outside of the thread->comm_lock critical
section, and the perf
process_thread may called comm__free() concurrently, cause this segfault
problem.
The process is as follows:
display_thread process_thread
-------------- --------------
thread__comm_len
-> thread__comm_str
# held the comm read lock
-> __thread__comm_str(thread)
# release the comm read lock
thread__delete
# held the comm
write lock
-> comm__free
->
comm_str__put(comm->comm_str)
-> zfree(&cs->str)
# release the comm
write lock
# The memory of the string pointed
to by comm has been free.
-> thread->comm_len = strlen(comm);
This patch expand the critical section range of thread->comm_lock in
thread__comm_len(),
to make strlen() called safe.
Signed-off-by: Wenyu Liu <liuwenyu7@...wei.com>
---
tools/perf/util/thread.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index e3e5427e1c3c..a2490a20eb56 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -311,17 +311,30 @@ const char *thread__comm_str(struct thread *thread)
return str;
}
+static int __thread__comm_len(struct thread *thread, const char *comm)
+{
+ if (!comm)
+ return 0;
+ thread->comm_len = strlen(comm);
+
+ return thread->comm_len;
+}
+
/* CHECKME: it should probably better return the max comm len from its
comm list */
int thread__comm_len(struct thread *thread)
{
- if (!thread->comm_len) {
- const char *comm = thread__comm_str(thread);
- if (!comm)
- return 0;
- thread->comm_len = strlen(comm);
+ int comm_len = thread->comm_len;
+
+ if (!comm_len) {
+ const char *comm;
+
+ down_read(&thread->comm_lock);
+ comm = __thread__comm_str(thread);
+ comm_len = __thread__comm_len(thread, comm);
+ up_read(&thread->comm_lock);
}
- return thread->comm_len;
+ return comm_len;
}
size_t thread__fprintf(struct thread *thread, FILE *fp)
--
2.36.1
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