Messages in this thread | | | Date | Wed, 15 Mar 2023 10:30:49 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v2 RESEND] perf top: Fix rare segfault in thread__comm_len() |
| |
Em Wed, Mar 15, 2023 at 02:42:17PM +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.
Applied, next time you resend a patch just to fix formatting, without changing what the patch does, please collect tags provided for the previous version, like the one from Namhyung:
Acked-by: Namhyung Kim <namhyung@kernel.org>
I did it because I saw it for v1, so added now.
Thanks,
- Arnaldo
> 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@entry=0x55ad1772bfe0, prog=0x0, > use_callchain=false, cb=cb@entry=0x0, cb_arg=0x0) at util/hist.c:1926 > #5 0x000055ad15d530a4 in evsel__output_resort_cb (evsel=evsel@entry=0x55ad1772bde0, > prog=prog@entry=0x0, cb=cb@entry=0x0, cb_arg=cb_arg@entry=0x0) at util/hist.c:1945 > #6 0x000055ad15d53110 in evsel__output_resort (evsel=evsel@entry=0x55ad1772bde0, > prog=prog@entry=0x0) at util/hist.c:1950 > #7 0x000055ad15c6ae9a in perf_top__resort_hists (t=t@entry=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@huawei.com> > --- > v1 -> v2 > - format the patch to be applied > > 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
--
- Arnaldo
| |