Re: [PATCH] libperf evsel: Make use of FD robust.

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Aug 18, 2021 at 10:47:07PM -0700, Ian Rogers escreveu:
> FD uses xyarray__entry that may return NULL if an index is out of
> bounds. If NULL is returned then a segv happens as FD unconditionally
> dereferences the pointer. This was happening in a case of with perf
> iostat as shown below. The fix is to make FD an "int*" rather than an
> int and handle the NULL case as either invalid input or a closed fd.
> 
> $ sudo gdb --args perf stat --iostat  list
> ...
> Breakpoint 1, perf_evsel__alloc_fd (evsel=0x5555560951a0, ncpus=1, nthreads=1) at evsel.c:50
> 50      {
> (gdb) bt
>  #0  perf_evsel__alloc_fd (evsel=0x5555560951a0, ncpus=1, nthreads=1) at evsel.c:50
>  #1  0x000055555585c188 in evsel__open_cpu (evsel=0x5555560951a0, cpus=0x555556093410,
>     threads=0x555556086fb0, start_cpu=0, end_cpu=1) at util/evsel.c:1792
>  #2  0x000055555585cfb2 in evsel__open (evsel=0x5555560951a0, cpus=0x0, threads=0x555556086fb0)
>     at util/evsel.c:2045
>  #3  0x000055555585d0db in evsel__open_per_thread (evsel=0x5555560951a0, threads=0x555556086fb0)
>     at util/evsel.c:2065
>  #4  0x00005555558ece64 in create_perf_stat_counter (evsel=0x5555560951a0,
>     config=0x555555c34700 <stat_config>, target=0x555555c2f1c0 <target>, cpu=0) at util/stat.c:590
>  #5  0x000055555578e927 in __run_perf_stat (argc=1, argv=0x7fffffffe4a0, run_idx=0)
>     at builtin-stat.c:833
>  #6  0x000055555578f3c6 in run_perf_stat (argc=1, argv=0x7fffffffe4a0, run_idx=0)
>     at builtin-stat.c:1048
>  #7  0x0000555555792ee5 in cmd_stat (argc=1, argv=0x7fffffffe4a0) at builtin-stat.c:2534
>  #8  0x0000555555835ed3 in run_builtin (p=0x555555c3f540 <commands+288>, argc=3,
>     argv=0x7fffffffe4a0) at perf.c:313
>  #9  0x0000555555836154 in handle_internal_command (argc=3, argv=0x7fffffffe4a0) at perf.c:365
>  #10 0x000055555583629f in run_argv (argcp=0x7fffffffe2ec, argv=0x7fffffffe2e0) at perf.c:409
>  #11 0x0000555555836692 in main (argc=3, argv=0x7fffffffe4a0) at perf.c:539
> ...
> (gdb) c
> Continuing.
> Error:
> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (uncore_iio_0/event=0x83,umask=0x04,ch_mask=0xF,fc_mask=0x07/).
> /bin/dmesg | grep -i perf may provide additional information.
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x00005555559b03ea in perf_evsel__close_fd_cpu (evsel=0x5555560951a0, cpu=1) at evsel.c:166
> 166                     if (FD(evsel, cpu, thread) >= 0)

Humm

static void perf_evsel__close_fd_cpu(struct perf_evsel *evsel, int cpu)
{
        int thread;

        for (thread = 0; thread < xyarray__max_y(evsel->fd); ++thread) {
                if (FD(evsel, cpu, thread) >= 0)
                        close(FD(evsel, cpu, thread));
                FD(evsel, cpu, thread) = -1;
        }
}

void perf_evsel__close_fd(struct perf_evsel *evsel)
{
        int cpu;

        for (cpu = 0; cpu < xyarray__max_x(evsel->fd); cpu++)
                perf_evsel__close_fd_cpu(evsel, cpu);
}

Isn't bounds checking being performed by the callers?

- Arnaldo

 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/lib/perf/evsel.c | 64 +++++++++++++++++++++++++++---------------
>  1 file changed, 41 insertions(+), 23 deletions(-)
> 
> diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
> index d8886720e83d..ede7af4d183c 100644
> --- a/tools/lib/perf/evsel.c
> +++ b/tools/lib/perf/evsel.c
> @@ -43,7 +43,7 @@ void perf_evsel__delete(struct perf_evsel *evsel)
>  	free(evsel);
>  }
>  
> -#define FD(e, x, y) (*(int *) xyarray__entry(e->fd, x, y))
> +#define FD(e, x, y) (int *) xyarray__entry(e->fd, x, y)
>  #define MMAP(e, x, y) (e->mmap ? ((struct perf_mmap *) xyarray__entry(e->mmap, x, y)) : NULL)
>  
>  int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)
> @@ -54,7 +54,10 @@ int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)
>  		int cpu, thread;
>  		for (cpu = 0; cpu < ncpus; cpu++) {
>  			for (thread = 0; thread < nthreads; thread++) {
> -				FD(evsel, cpu, thread) = -1;
> +				int *fd = FD(evsel, cpu, thread);
> +
> +				if (fd)
> +					 *fd = -1;
>  			}
>  		}
>  	}
> @@ -80,7 +83,7 @@ sys_perf_event_open(struct perf_event_attr *attr,
>  static int get_group_fd(struct perf_evsel *evsel, int cpu, int thread, int *group_fd)
>  {
>  	struct perf_evsel *leader = evsel->leader;
> -	int fd;
> +	int *fd;
>  
>  	if (evsel == leader) {
>  		*group_fd = -1;
> @@ -95,10 +98,10 @@ static int get_group_fd(struct perf_evsel *evsel, int cpu, int thread, int *grou
>  		return -ENOTCONN;
>  
>  	fd = FD(leader, cpu, thread);
> -	if (fd == -1)
> +	if (fd == NULL || *fd == -1)
>  		return -EBADF;
>  
> -	*group_fd = fd;
> +	*group_fd = *fd;
>  
>  	return 0;
>  }
> @@ -138,7 +141,11 @@ int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *cpus,
>  
>  	for (cpu = 0; cpu < cpus->nr; cpu++) {
>  		for (thread = 0; thread < threads->nr; thread++) {
> -			int fd, group_fd;
> +			int fd, group_fd, *evsel_fd;
> +
> +			evsel_fd = FD(evsel, cpu, thread);
> +			if (evsel_fd == NULL)
> +				return -EINVAL;
>  
>  			err = get_group_fd(evsel, cpu, thread, &group_fd);
>  			if (err < 0)
> @@ -151,7 +158,7 @@ int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *cpus,
>  			if (fd < 0)
>  				return -errno;
>  
> -			FD(evsel, cpu, thread) = fd;
> +			*evsel_fd = fd;
>  		}
>  	}
>  
> @@ -163,9 +170,12 @@ static void perf_evsel__close_fd_cpu(struct perf_evsel *evsel, int cpu)
>  	int thread;
>  
>  	for (thread = 0; thread < xyarray__max_y(evsel->fd); ++thread) {
> -		if (FD(evsel, cpu, thread) >= 0)
> -			close(FD(evsel, cpu, thread));
> -		FD(evsel, cpu, thread) = -1;
> +		int *fd = FD(evsel, cpu, thread);
> +
> +		if (fd && *fd >= 0) {
> +			close(*fd);
> +			*fd = -1;
> +		}
>  	}
>  }
>  
> @@ -209,13 +219,12 @@ void perf_evsel__munmap(struct perf_evsel *evsel)
>  
>  	for (cpu = 0; cpu < xyarray__max_x(evsel->fd); cpu++) {
>  		for (thread = 0; thread < xyarray__max_y(evsel->fd); thread++) {
> -			int fd = FD(evsel, cpu, thread);
> -			struct perf_mmap *map = MMAP(evsel, cpu, thread);
> +			int *fd = FD(evsel, cpu, thread);
>  
> -			if (fd < 0)
> +			if (fd == NULL || *fd < 0)
>  				continue;
>  
> -			perf_mmap__munmap(map);
> +			perf_mmap__munmap(MMAP(evsel, cpu, thread));
>  		}
>  	}
>  
> @@ -239,15 +248,16 @@ int perf_evsel__mmap(struct perf_evsel *evsel, int pages)
>  
>  	for (cpu = 0; cpu < xyarray__max_x(evsel->fd); cpu++) {
>  		for (thread = 0; thread < xyarray__max_y(evsel->fd); thread++) {
> -			int fd = FD(evsel, cpu, thread);
> -			struct perf_mmap *map = MMAP(evsel, cpu, thread);
> +			int *fd = FD(evsel, cpu, thread);
> +			struct perf_mmap *map;
>  
> -			if (fd < 0)
> +			if (fd == NULL || *fd < 0)
>  				continue;
>  
> +			map = MMAP(evsel, cpu, thread);
>  			perf_mmap__init(map, NULL, false, NULL);
>  
> -			ret = perf_mmap__mmap(map, &mp, fd, cpu);
> +			ret = perf_mmap__mmap(map, &mp, *fd, cpu);
>  			if (ret) {
>  				perf_evsel__munmap(evsel);
>  				return ret;
> @@ -260,7 +270,9 @@ int perf_evsel__mmap(struct perf_evsel *evsel, int pages)
>  
>  void *perf_evsel__mmap_base(struct perf_evsel *evsel, int cpu, int thread)
>  {
> -	if (FD(evsel, cpu, thread) < 0 || MMAP(evsel, cpu, thread) == NULL)
> +	int *fd = FD(evsel, cpu, thread);
> +
> +	if (fd == NULL || *fd < 0 || MMAP(evsel, cpu, thread) == NULL)
>  		return NULL;
>  
>  	return MMAP(evsel, cpu, thread)->base;
> @@ -295,17 +307,18 @@ int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread,
>  		     struct perf_counts_values *count)
>  {
>  	size_t size = perf_evsel__read_size(evsel);
> +	int *fd = FD(evsel, cpu, thread);
>  
>  	memset(count, 0, sizeof(*count));
>  
> -	if (FD(evsel, cpu, thread) < 0)
> +	if (fd == NULL || *fd < 0)
>  		return -EINVAL;
>  
>  	if (MMAP(evsel, cpu, thread) &&
>  	    !perf_mmap__read_self(MMAP(evsel, cpu, thread), count))
>  		return 0;
>  
> -	if (readn(FD(evsel, cpu, thread), count->values, size) <= 0)
> +	if (readn(*fd, count->values, size) <= 0)
>  		return -errno;
>  
>  	return 0;
> @@ -318,8 +331,13 @@ static int perf_evsel__run_ioctl(struct perf_evsel *evsel,
>  	int thread;
>  
>  	for (thread = 0; thread < xyarray__max_y(evsel->fd); thread++) {
> -		int fd = FD(evsel, cpu, thread),
> -		    err = ioctl(fd, ioc, arg);
> +		int err;
> +		int *fd = FD(evsel, cpu, thread);
> +
> +		if (fd || *fd < 0)
> +			return -1;
> +
> +		err = ioctl(*fd, ioc, arg);
>  
>  		if (err)
>  			return err;
> -- 
> 2.33.0.rc1.237.g0d66db33f3-goog

-- 

- Arnaldo