[PATCH] perf buildid: fix off-by-one in write_buildid()

[PATCH] perf buildid: fix off-by-one in write_buildid()

[Andrey Ryabinin]

write_buildid() increments 'name_len' with intention to take into account
trailing zero byte. However, 'name_len' was already incremented in
machine__write_buildid_table() before.
So this leads to out-of-bounds read in do_write():

$ ./perf record sleep 0
[ perf record: Woken up 1 times to write data ]
=================================================================
==15899==ERROR: AddressSanitizer: global-buffer-overflow on address 0x00000099fc92 at pc 0x7f1aa9c7eab5 bp 0x7fff940f84d0 sp 0x7fff940f7c78
READ of size 19 at 0x00000099fc92 thread T0
    #0 0x7f1aa9c7eab4  (/usr/lib/gcc/x86_64-pc-linux-gnu/5.3.0/libasan.so.2+0x44ab4)
    #1 0x649c5b in do_write util/header.c:67
    #2 0x649c5b in write_padded util/header.c:82
    #3 0x57e8bc in write_buildid util/build-id.c:239
    #4 0x57e8bc in machine__write_buildid_table util/build-id.c:278
...

0x00000099fc92 is located 0 bytes to the right of global variable '*.LC99' defined in 'util/symbol.c' (0x99fc80) of size 18
  '*.LC99' is ascii string '[kernel.kallsyms]'
...

Shadow bytes around the buggy address:
  0x00008012bf80: f9 f9 f9 f9 00 00 00 00 00 00 03 f9 f9 f9 f9 f9
=>0x00008012bf90: 00 00[02]f9 f9 f9 f9 f9 00 00 00 00 00 05 f9 f9
  0x00008012bfa0: f9 f9 f9 f9 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
 tools/perf/util/build-id.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 0573c2e..a1ff68b 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -235,7 +235,7 @@ static int write_buildid(const char *name, size_t name_len, u8 *build_id,
 	if (err < 0)
 		return err;
 
-	return write_padded(fd, name, name_len + 1, len);
+	return write_padded(fd, name, name_len, len);
 }
 
 static int machine__write_buildid_table(struct machine *machine, int fd)
-- 
2.7.3

Re: [PATCH] perf buildid: fix off-by-one in write_buildid()

[Arnaldo Carvalho de Melo]

Em Tue, Apr 19, 2016 at 11:17:27AM +0300, Andrey Ryabinin escreveu:
> write_buildid() increments 'name_len' with intention to take into account
> trailing zero byte. However, 'name_len' was already incremented in
> machine__write_buildid_table() before.
> So this leads to out-of-bounds read in do_write():

Could we keep the assumptions that for a string 's' the length is
strlen(s) and that when we want to write a string _with_ its trailing
'\0' we should use strlen(s) + 1?

I.e. I propose this patch instead, ok?

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 0573c2ec861d..b6ecf87bc3e3 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -261,14 +261,14 @@ static int machine__write_buildid_table(struct machine *machine, int fd)
 
 		if (dso__is_vdso(pos)) {
 			name = pos->short_name;
-			name_len = pos->short_name_len + 1;
+			name_len = pos->short_name_len;
 		} else if (dso__is_kcore(pos)) {
 			machine__mmap_name(machine, nm, sizeof(nm));
 			name = nm;
-			name_len = strlen(nm) + 1;
+			name_len = strlen(nm);
 		} else {
 			name = pos->long_name;
-			name_len = pos->long_name_len + 1;
+			name_len = pos->long_name_len;
 		}
 
 		in_kernel = pos->kernel ||
 
> $ ./perf record sleep 0
> [ perf record: Woken up 1 times to write data ]
> =================================================================
> ==15899==ERROR: AddressSanitizer: global-buffer-overflow on address 0x00000099fc92 at pc 0x7f1aa9c7eab5 bp 0x7fff940f84d0 sp 0x7fff940f7c78
> READ of size 19 at 0x00000099fc92 thread T0
>     #0 0x7f1aa9c7eab4  (/usr/lib/gcc/x86_64-pc-linux-gnu/5.3.0/libasan.so.2+0x44ab4)
>     #1 0x649c5b in do_write util/header.c:67
>     #2 0x649c5b in write_padded util/header.c:82
>     #3 0x57e8bc in write_buildid util/build-id.c:239
>     #4 0x57e8bc in machine__write_buildid_table util/build-id.c:278
> ...
> 
> 0x00000099fc92 is located 0 bytes to the right of global variable '*.LC99' defined in 'util/symbol.c' (0x99fc80) of size 18
>   '*.LC99' is ascii string '[kernel.kallsyms]'
> ...
> 
> Shadow bytes around the buggy address:
>   0x00008012bf80: f9 f9 f9 f9 00 00 00 00 00 00 03 f9 f9 f9 f9 f9
> =>0x00008012bf90: 00 00[02]f9 f9 f9 f9 f9 00 00 00 00 00 05 f9 f9
>   0x00008012bfa0: f9 f9 f9 f9 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> ---
>  tools/perf/util/build-id.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> index 0573c2e..a1ff68b 100644
> --- a/tools/perf/util/build-id.c
> +++ b/tools/perf/util/build-id.c
> @@ -235,7 +235,7 @@ static int write_buildid(const char *name, size_t name_len, u8 *build_id,
>  	if (err < 0)
>  		return err;
>  
> -	return write_padded(fd, name, name_len + 1, len);
> +	return write_padded(fd, name, name_len, len);
>  }
>  
>  static int machine__write_buildid_table(struct machine *machine, int fd)
> -- 
> 2.7.3

Re: [PATCH] perf buildid: fix off-by-one in write_buildid()

[Arnaldo Carvalho de Melo]

Em Tue, Apr 19, 2016 at 11:17:27AM +0300, Andrey Ryabinin escreveu:
> write_buildid() increments 'name_len' with intention to take into account
> trailing zero byte. However, 'name_len' was already incremented in
> machine__write_buildid_table() before.
> So this leads to out-of-bounds read in do_write():

Adrian, can you please take a look at the db-export improvements made in
this series? It'd be good to have your ack for those,

thanks!

- Arnaldo
 
> $ ./perf record sleep 0
> [ perf record: Woken up 1 times to write data ]
> =================================================================
> ==15899==ERROR: AddressSanitizer: global-buffer-overflow on address 0x00000099fc92 at pc 0x7f1aa9c7eab5 bp 0x7fff940f84d0 sp 0x7fff940f7c78
> READ of size 19 at 0x00000099fc92 thread T0
>     #0 0x7f1aa9c7eab4  (/usr/lib/gcc/x86_64-pc-linux-gnu/5.3.0/libasan.so.2+0x44ab4)
>     #1 0x649c5b in do_write util/header.c:67
>     #2 0x649c5b in write_padded util/header.c:82
>     #3 0x57e8bc in write_buildid util/build-id.c:239
>     #4 0x57e8bc in machine__write_buildid_table util/build-id.c:278
> ...
> 
> 0x00000099fc92 is located 0 bytes to the right of global variable '*.LC99' defined in 'util/symbol.c' (0x99fc80) of size 18
>   '*.LC99' is ascii string '[kernel.kallsyms]'
> ...
> 
> Shadow bytes around the buggy address:
>   0x00008012bf80: f9 f9 f9 f9 00 00 00 00 00 00 03 f9 f9 f9 f9 f9
> =>0x00008012bf90: 00 00[02]f9 f9 f9 f9 f9 00 00 00 00 00 05 f9 f9
>   0x00008012bfa0: f9 f9 f9 f9 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> ---
>  tools/perf/util/build-id.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> index 0573c2e..a1ff68b 100644
> --- a/tools/perf/util/build-id.c
> +++ b/tools/perf/util/build-id.c
> @@ -235,7 +235,7 @@ static int write_buildid(const char *name, size_t name_len, u8 *build_id,
>  	if (err < 0)
>  		return err;
>  
> -	return write_padded(fd, name, name_len + 1, len);
> +	return write_padded(fd, name, name_len, len);
>  }
>  
>  static int machine__write_buildid_table(struct machine *machine, int fd)
> -- 
> 2.7.3

Re: [PATCH] perf buildid: fix off-by-one in write_buildid()

[Andrey Ryabinin]

On 04/19/2016 04:38 PM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Apr 19, 2016 at 11:17:27AM +0300, Andrey Ryabinin escreveu:
>> write_buildid() increments 'name_len' with intention to take into account
>> trailing zero byte. However, 'name_len' was already incremented in
>> machine__write_buildid_table() before.
>> So this leads to out-of-bounds read in do_write():
> 
> Could we keep the assumptions that for a string 's' the length is
> strlen(s) and that when we want to write a string _with_ its trailing
> '\0' we should use strlen(s) + 1?
> 
> I.e. I propose this patch instead, ok?
> 

Yup, looks good. Thanks.

> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> index 0573c2ec861d..b6ecf87bc3e3 100644
> --- a/tools/perf/util/build-id.c
> +++ b/tools/perf/util/build-id.c
> @@ -261,14 +261,14 @@ static int machine__write_buildid_table(struct machine *machine, int fd)
>  
>  		if (dso__is_vdso(pos)) {
>  			name = pos->short_name;
> -			name_len = pos->short_name_len + 1;
> +			name_len = pos->short_name_len;
>  		} else if (dso__is_kcore(pos)) {
>  			machine__mmap_name(machine, nm, sizeof(nm));
>  			name = nm;
> -			name_len = strlen(nm) + 1;
> +			name_len = strlen(nm);
>  		} else {
>  			name = pos->long_name;
> -			name_len = pos->long_name_len + 1;
> +			name_len = pos->long_name_len;
>  		}
>  
>  		in_kernel = pos->kernel ||
>  

Re: [PATCH] perf buildid: fix off-by-one in write_buildid()

[Adrian Hunter]

On 19/04/16 16:40, Arnaldo Carvalho de Melo wrote:
> Em Tue, Apr 19, 2016 at 11:17:27AM +0300, Andrey Ryabinin escreveu:
>> write_buildid() increments 'name_len' with intention to take into account
>> trailing zero byte. However, 'name_len' was already incremented in
>> machine__write_buildid_table() before.
>> So this leads to out-of-bounds read in do_write():
> 
> Adrian, can you please take a look at the db-export improvements made in
> this series? It'd be good to have your ack for those,

You mean the patches from Chris Phlipot - yes I'll look at them.

> 
> thanks!
> 
> - Arnaldo
>  
>> $ ./perf record sleep 0
>> [ perf record: Woken up 1 times to write data ]
>> =================================================================
>> ==15899==ERROR: AddressSanitizer: global-buffer-overflow on address 0x00000099fc92 at pc 0x7f1aa9c7eab5 bp 0x7fff940f84d0 sp 0x7fff940f7c78
>> READ of size 19 at 0x00000099fc92 thread T0
>>     #0 0x7f1aa9c7eab4  (/usr/lib/gcc/x86_64-pc-linux-gnu/5.3.0/libasan.so.2+0x44ab4)
>>     #1 0x649c5b in do_write util/header.c:67
>>     #2 0x649c5b in write_padded util/header.c:82
>>     #3 0x57e8bc in write_buildid util/build-id.c:239
>>     #4 0x57e8bc in machine__write_buildid_table util/build-id.c:278
>> ...
>>
>> 0x00000099fc92 is located 0 bytes to the right of global variable '*.LC99' defined in 'util/symbol.c' (0x99fc80) of size 18
>>   '*.LC99' is ascii string '[kernel.kallsyms]'
>> ...
>>
>> Shadow bytes around the buggy address:
>>   0x00008012bf80: f9 f9 f9 f9 00 00 00 00 00 00 03 f9 f9 f9 f9 f9
>> =>0x00008012bf90: 00 00[02]f9 f9 f9 f9 f9 00 00 00 00 00 05 f9 f9
>>   0x00008012bfa0: f9 f9 f9 f9 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00
>>
>> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> ---
>>  tools/perf/util/build-id.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
>> index 0573c2e..a1ff68b 100644
>> --- a/tools/perf/util/build-id.c
>> +++ b/tools/perf/util/build-id.c
>> @@ -235,7 +235,7 @@ static int write_buildid(const char *name, size_t name_len, u8 *build_id,
>>  	if (err < 0)
>>  		return err;
>>  
>> -	return write_padded(fd, name, name_len + 1, len);
>> +	return write_padded(fd, name, name_len, len);
>>  }
>>  
>>  static int machine__write_buildid_table(struct machine *machine, int fd)
>> -- 
>> 2.7.3
> 

Re: [PATCH] perf buildid: fix off-by-one in write_buildid()

[Arnaldo Carvalho de Melo]

Em Wed, Apr 20, 2016 at 03:36:22PM +0300, Adrian Hunter escreveu:
> On 19/04/16 16:40, Arnaldo Carvalho de Melo wrote:
> > Em Tue, Apr 19, 2016 at 11:17:27AM +0300, Andrey Ryabinin escreveu:
> >> write_buildid() increments 'name_len' with intention to take into account
> >> trailing zero byte. However, 'name_len' was already incremented in
> >> machine__write_buildid_table() before.
> >> So this leads to out-of-bounds read in do_write():
> > 
> > Adrian, can you please take a look at the db-export improvements made in
> > this series? It'd be good to have your ack for those,
> 
> You mean the patches from Chris Phlipot - yes I'll look at them.

Yeah, thanks,

- Arnaldo

[tip:perf/core] perf buildid: Fix off-by-one in write_buildid()

[tip-bot for Andrey Ryabinin]

Commit-ID:  70a2cba972e5e4a5d850e4179381f1cd344c6828
Gitweb:     http://git.kernel.org/tip/70a2cba972e5e4a5d850e4179381f1cd344c6828
Author:     Andrey Ryabinin <aryabinin@virtuozzo.com>
AuthorDate: Tue, 19 Apr 2016 11:17:27 +0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 25 Apr 2016 12:49:16 -0300

perf buildid: Fix off-by-one in write_buildid()

write_buildid() increments 'name_len' with intention to take into
account trailing zero byte. However, 'name_len' was already incremented
in machine__write_buildid_table() before.  So this leads to
out-of-bounds read in do_write():

  $ ./perf record sleep 0
  [ perf record: Woken up 1 times to write data ]
  =================================================================
  ==15899==ERROR: AddressSanitizer: global-buffer-overflow on address 0x00000099fc92 at pc 0x7f1aa9c7eab5 bp 0x7fff940f84d0 sp 0x7fff940f7c78
  READ of size 19 at 0x00000099fc92 thread T0
      #0 0x7f1aa9c7eab4  (/usr/lib/gcc/x86_64-pc-linux-gnu/5.3.0/libasan.so.2+0x44ab4)
      #1 0x649c5b in do_write util/header.c:67
      #2 0x649c5b in write_padded util/header.c:82
      #3 0x57e8bc in write_buildid util/build-id.c:239
      #4 0x57e8bc in machine__write_buildid_table util/build-id.c:278
  ...

  0x00000099fc92 is located 0 bytes to the right of global variable '*.LC99' defined in 'util/symbol.c' (0x99fc80) of size 18
    '*.LC99' is ascii string '[kernel.kallsyms]'
  ...

  Shadow bytes around the buggy address:
    0x00008012bf80: f9 f9 f9 f9 00 00 00 00 00 00 03 f9 f9 f9 f9 f9
  =>0x00008012bf90: 00 00[02]f9 f9 f9 f9 f9 00 00 00 00 00 05 f9 f9
    0x00008012bfa0: f9 f9 f9 f9 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1461053847-5633-1-git-send-email-aryabinin@virtuozzo.com
[ Remove the off-by one at the origin, to keep len(s) == strlen(s) assumption ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/build-id.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 0573c2e..b6ecf87 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -261,14 +261,14 @@ static int machine__write_buildid_table(struct machine *machine, int fd)
 
 		if (dso__is_vdso(pos)) {
 			name = pos->short_name;
-			name_len = pos->short_name_len + 1;
+			name_len = pos->short_name_len;
 		} else if (dso__is_kcore(pos)) {
 			machine__mmap_name(machine, nm, sizeof(nm));
 			name = nm;
-			name_len = strlen(nm) + 1;
+			name_len = strlen(nm);
 		} else {
 			name = pos->long_name;
-			name_len = pos->long_name_len + 1;
+			name_len = pos->long_name_len;
 		}
 
 		in_kernel = pos->kernel ||