2019-07-25 18:31:08

by Vince Weaver

Subject: [patch] perf report segfault with 0-sized strings

Hello,

the perf_data_fuzzer found an issue when strings have size 0.
malloc() in do_read_string() is happy to allocate a string of
size 0 but when code (in this case the pmu parser) tries to work with
those it will segfault.

Signed-off-by: Vince Weaver <[email protected]>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c24db7f4909c..641129efa987 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -251,6 +252,9 @@ static char *do_read_string(struct feat_fd *ff)
if (do_read_u32(ff, &len))
return NULL;

+ if (len==0)
+ return NULL;
+
buf = malloc(len);
if (!buf)
return NULL;
@@ -1781,6 +1785,10 @@ static void print_pmu_mappings(struct feat_fd *ff, FILE *fp)
str = ff->ph->env.pmu_mappings;

while (pmu_num) {
+
+ if (str==NULL)
+ goto error;
+
type = strtoul(str, &tmp, 0);
if (*tmp != ':')
goto error;

2019-07-25 19:05:34

by Vince Weaver

Subject: Re: [patch] perf report segfault with 0-sized strings

probably all perf_header_strings are affected by this. The fuzzer just
tripped up cmdline now, which needs this fix.

Signed-off-by: Vince Weaver <[email protected]>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c24db7f4909c..631aa1911f3a 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1427,6 +1430,8 @@ static void print_cmdline(struct feat_fd *ff, FILE *fp)

fprintf(fp, "# cmdline : ");

+ if (ff->ph->env.cmdline_argv==NULL) return;
+
for (i = 0; i < nr; i++) {
char *argv_i = strdup(ff->ph->env.cmdline_argv[i]);
if (!argv_i) {

2019-07-26 19:55:57

by Arnaldo Carvalho de Melo

Subject: Re: [patch] perf report segfault with 0-sized strings

Em Thu, Jul 25, 2019 at 02:27:14PM -0400, Vince Weaver escreveu:
> Hello,
>
> the perf_data_fuzzer found an issue when strings have size 0.
> malloc() in do_read_string() is happy to allocate a string of
> size 0 but when code (in this case the pmu parser) tries to work with
> those it will segfault.

So here are two fixes, i.e. one is to make do_read_string() to return
NULL when len is 0, which do_read_string() already returns for failure
(NULL) and most of the callers I looked handle that.

The other is to make print_pmu_mappings() deal with a NULL
ff->ph->env.pmu_mappings, agreed?

- Arnaldo

> Signed-off-by: Vince Weaver <[email protected]>
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index c24db7f4909c..641129efa987 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -251,6 +252,9 @@ static char *do_read_string(struct feat_fd *ff)
> if (do_read_u32(ff, &len))
> return NULL;
>
> + if (len==0)
> + return NULL;
> +
> buf = malloc(len);
> if (!buf)
> return NULL;
> @@ -1781,6 +1785,10 @@ static void print_pmu_mappings(struct feat_fd *ff, FILE *fp)
> str = ff->ph->env.pmu_mappings;
>
> while (pmu_num) {
> +
> + if (str==NULL)
> + goto error;
> +
> type = strtoul(str, &tmp, 0);
> if (*tmp != ':')
> goto error;

--

- Arnaldo

2019-07-26 19:56:32

by Arnaldo Carvalho de Melo

Subject: Re: [patch] perf report segfault with 0-sized strings

Em Thu, Jul 25, 2019 at 03:04:32PM -0400, Vince Weaver escreveu:
>
> probably all perf_header_strings are affected by this. The fuzzer just
> tripped up cmdline now, which needs this fix.

I think we have to catch this earlier, i.e. when processing each
feature, lemme check...

- Arnaldo

> Signed-off-by: Vince Weaver <[email protected]>
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index c24db7f4909c..631aa1911f3a 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1427,6 +1430,8 @@ static void print_cmdline(struct feat_fd *ff, FILE *fp)
>
> fprintf(fp, "# cmdline : ");
>
> + if (ff->ph->env.cmdline_argv==NULL) return;
> +
> for (i = 0; i < nr; i++) {
> char *argv_i = strdup(ff->ph->env.cmdline_argv[i]);
> if (!argv_i) {

--

- Arnaldo