lkml.org 
[lkml]   [2018]   [Sep]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 71/77] perf augmented_syscalls: Check probe_read_str() return separately
Date
From: Arnaldo Carvalho de Melo <acme@redhat.com>

Using a value returned from probe_read_str() to tell how many bytes to
copy using perf_event_output() has issues in some older kernels, like
4.17.17-100.fc27.x86_64, so separate the bounds checking done on how
many bytes to copy to a separate variable, so that the next patch has
only what is being done to make the test pass on older BPF validators.

For reference, see the discussion in this thread:

https://www.spinics.net/lists/netdev/msg480099.html

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-jtsapwibyxrnv1xjfsgzp0fj@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/examples/bpf/augmented_syscalls.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/perf/examples/bpf/augmented_syscalls.c b/tools/perf/examples/bpf/augmented_syscalls.c
index 1419a9186937..0decbcfa8b90 100644
--- a/tools/perf/examples/bpf/augmented_syscalls.c
+++ b/tools/perf/examples/bpf/augmented_syscalls.c
@@ -33,9 +33,9 @@ struct syscall_exit_args {
};

struct augmented_filename {
- int size;
- int reserved;
- char value[256];
+ unsigned int size;
+ int reserved;
+ char value[256];
};

#define augmented_filename_syscall(syscall) \
@@ -46,14 +46,15 @@ struct augmented_enter_##syscall##_args { \
int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args) \
{ \
struct augmented_enter_##syscall##_args augmented_args = { .filename.reserved = 0, }; \
+ unsigned int len = sizeof(augmented_args); \
probe_read(&augmented_args.args, sizeof(augmented_args.args), args); \
augmented_args.filename.size = probe_read_str(&augmented_args.filename.value, \
sizeof(augmented_args.filename.value), \
args->filename_ptr); \
+ if (augmented_args.filename.size < sizeof(augmented_args.filename.value)) \
+ len -= sizeof(augmented_args.filename.value) - augmented_args.filename.size; \
perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \
- &augmented_args, \
- (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \
- augmented_args.filename.size)); \
+ &augmented_args, len); \
return 0; \
} \
int syscall_exit(syscall)(struct syscall_exit_args *args) \
--
2.14.4
\
 
 \ /
  Last update: 2018-09-06 00:08    [W:0.219 / U:5.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site