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Message-ID: <bce3b92c-8346-6fc5-c408-0afb2c7395d5@huawei.com>
Date: Tue, 7 Mar 2023 11:35:16 +0800
From: "liuwenyu (D)" <liuwenyu7@...wei.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
CC: <peterz@...radead.org>, <mingo@...hat.com>, <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>, <linfeilong@...wei.com>,
"hewenliang (C)" <hewenliang4@...wei.com>, <yeyunfeng@...wei.com>
Subject: Re: [PATCH] perf top: Fix rare segfault in thread__comm_len()
Sorry, the patch was sent in an incorrect format due to my email client configuration. I'll resubmit a v2 version patch soon.
在 2023/3/7 4:28, Arnaldo Carvalho de Melo 写道:
> Em Fri, Mar 03, 2023 at 06:02:17PM +0800, liuwenyu (D) escreveu:
>> 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.
>
> The patch isn't applying, please check this and resubmit, the first
> issue is that it is malformed at that CHECKME comment, that is broken in
> two lines, I fixed that and tried again, still doesn't apply:
>
> ⬢[acme@...lbox perf-tools]$ patch -p1 < ./20230303_liuwenyu7_perf_top_fix_rare_segfault_in_thread__comm_len.mbx
> patching file tools/perf/util/thread.c
> Hunk #1 FAILED at 311.
> 1 out of 1 hunk FAILED -- saving rejects to file tools/perf/util/thread.c.rej
> ⬢[acme@...lbox perf-tools]$ cat tools/perf/util/thread.c.rej
> --- tools/perf/util/thread.c
> +++ 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)
> ⬢[acme@...lbox perf-tools]$
>
>
>
>> 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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