[patch] perf report segfault with 0-sized strings

[patch] perf report segfault with 0-sized strings

[Vince Weaver]

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 <vincent.weaver@maine.edu>

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;

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

[Vince Weaver]

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 <vincent.weaver@maine.edu>

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) {

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

[Arnaldo Carvalho de Melo]

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 <vincent.weaver@maine.edu>
> 
> 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

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

[Arnaldo Carvalho de Melo]

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 <vincent.weaver@maine.edu>
> 
> 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