[PATCH 09/28] perf trace: Fix segmentation fault when access syscall info on arm64

[Arnaldo Carvalho de Melo]

From: Leo Yan <leo.yan@xxxxxxxxxx>

'perf trace' reports the segmentation fault as below on Arm64:

  # perf trace -e string -e augmented_raw_syscalls.c
  LLVM: dumping tools/perf/examples/bpf/augmented_raw_syscalls.o
  perf: Segmentation fault
  Obtained 12 stack frames.
  perf(sighandler_dump_stack+0x47) [0xaaaaac96ac87]
  linux-vdso.so.1(+0x5b7) [0xffffadbeb5b7]
  /lib/aarch64-linux-gnu/libc.so.6(strlen+0x10) [0xfffface7d5d0]
  /lib/aarch64-linux-gnu/libc.so.6(_IO_vfprintf+0x1ac7) [0xfffface49f97]
  /lib/aarch64-linux-gnu/libc.so.6(__vsnprintf_chk+0xc7) [0xffffacedfbe7]
  perf(scnprintf+0x97) [0xaaaaac9ca3ff]
  perf(+0x997bb) [0xaaaaac8e37bb]
  perf(cmd_trace+0x28e7) [0xaaaaac8ec09f]
  perf(+0xd4a13) [0xaaaaac91ea13]
  perf(main+0x62f) [0xaaaaac8a147f]
  /lib/aarch64-linux-gnu/libc.so.6(__libc_start_main+0xe3) [0xfffface22d23]
  perf(+0x57723) [0xaaaaac8a1723]
  Segmentation fault

This issue is introduced by commit 30a910d7d3e0 ("perf trace:
Preallocate the syscall table"), it allocates trace->syscalls.table[]
array and the element count is 'trace->sctbl->syscalls.nr_entries'; but
on Arm64, the system call number is not continuously used; e.g. the
syscall maximum id is 436 but the real entries is only 281.

So the table is allocated with 'nr_entries' as the element count, but it
accesses the table with the syscall id, which might be out of the bound
of the array and cause the segmentation fault.

This patch allocates trace->syscalls.table[] with the element count is
'trace->sctbl->syscalls.max_id + 1', this allows any id to access the
table without out of the bound.

Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Martin KaFai Lau <kafai@xxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Yonghong Song <yhs@xxxxxx>
Fixes: 30a910d7d3e0 ("perf trace: Preallocate the syscall table")
Link: http://lkml.kernel.org/r/20190809104752.27338-1-leo.yan@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/builtin-trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 75eb3811e942..d553d06a9aeb 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1492,7 +1492,7 @@ static int trace__read_syscall_info(struct trace *trace, int id)
 	const char *name = syscalltbl__name(trace->sctbl, id);
 
 	if (trace->syscalls.table == NULL) {
-		trace->syscalls.table = calloc(trace->sctbl->syscalls.nr_entries, sizeof(*sc));
+		trace->syscalls.table = calloc(trace->sctbl->syscalls.max_id + 1, sizeof(*sc));
 		if (trace->syscalls.table == NULL)
 			return -ENOMEM;
 	}
-- 
2.21.0