[PATCH] Fix off by one in tools/perf strncpy size argument

[PATCH] Fix off by one in tools/perf strncpy size argument

[Dominik 'disconnect3d' Czarnota]

From: disconnect3d <dominik.b.czarnota@gmail.com>

This patch fixes an off-by-one error in strncpy size argument in
tools/perf/util/map.c. The issue is that in:

        strncmp(filename, "/system/lib/", 11)

the passed string literal: "/system/lib/" has 12 bytes (without the NULL
byte) and the passed size argument is 11. As a result, the logic won't
match the ending "/" byte and will pass filepaths that are stored in
other directories e.g. "/system/libmalicious/bin" or just
"/system/libmalicious".

This functionality seems to be present only on Android. I assume the
/system/ directory is only writable by the root user, so I don't
think this bug has much (or any) security impact.

Signed-off-by: disconnect3d <dominik.b.czarnota@gmail.com>
---

Notes:
    I can't test this patch, so if someone can, please, do so.
    
    The bug could also be fixed by changing the size argument to `sizeof("string literal")-1` but I am not proposing this change as that would have to be changed in other places.
    
    There are also more cases like this in kernel sources which I am going to report soon.
    
    Also please note that other path comparisons in this file lack the "/" at the end and it seems they may imply similar issue. I haven't analysed the code deeply to see if that is a real issue.
    
    This bug has been found by running a massive grep-like search using Google's BigQuery on GitHub repositories data. I am also going to work on a CodeQL/Semmle query to be able to find more sophisticated cases like this that can't be found via grepping.

 tools/perf/util/map.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index a08ca276098e..addd7edb0486 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -89,7 +89,7 @@ static inline bool replace_android_lib(const char *filename, char *newfilename)
 		return true;
 	}
 
-	if (!strncmp(filename, "/system/lib/", 11)) {
+	if (!strncmp(filename, "/system/lib/", 12)) {
 		char *ndk, *app;
 		const char *arch;
 		size_t ndk_length;
-- 
2.25.1

Re: [PATCH] Fix off by one in tools/perf strncpy size argument

[Arnaldo Carvalho de Melo]

Em Mon, Mar 09, 2020 at 11:48:53AM +0100, Dominik 'disconnect3d' Czarnota escreveu:
> From: disconnect3d <dominik.b.czarnota@gmail.com>
> 
> This patch fixes an off-by-one error in strncpy size argument in
> tools/perf/util/map.c. The issue is that in:
> 
>         strncmp(filename, "/system/lib/", 11)
> 
> the passed string literal: "/system/lib/" has 12 bytes (without the NULL
> byte) and the passed size argument is 11. As a result, the logic won't
> match the ending "/" byte and will pass filepaths that are stored in
> other directories e.g. "/system/libmalicious/bin" or just
> "/system/libmalicious".
> 
> This functionality seems to be present only on Android. I assume the
> /system/ directory is only writable by the root user, so I don't
> think this bug has much (or any) security impact.
> 
> Signed-off-by: disconnect3d <dominik.b.czarnota@gmail.com>
> ---
> 
> Notes:
>     I can't test this patch, so if someone can, please, do so.
>     
>     The bug could also be fixed by changing the size argument to `sizeof("string literal")-1` but I am not proposing this change as that would have to be changed in other places.

So, there are parts of this tools/perf/util/map.c that uses the idiom
you mention, for instance:

static inline int is_anon_memory(const char *filename, u32 flags)
{
        return flags & MAP_HUGETLB ||
               !strcmp(filename, "//anon") ||
               !strncmp(filename, "/dev/zero", sizeof("/dev/zero") - 1) ||
               !strncmp(filename, "/anon_hugepage", sizeof("/anon_hugepage") - 1);
}

So I think we should make all cases use this idim to avoid these
problems.

So I'll add your patch, then another, on top, that fixes the other
off-by-one errors introduced by the android specific code in this patch:

Fixes: eca818369996 ("perf tools: Add automatic remapping of Android libraries")

Put this in perf/urgent and then in perf/core move to the more robust
idiom,

Thanks,

- Arnaldo
     
>     There are also more cases like this in kernel sources which I am going to report soon.
>     
>     Also please note that other path comparisons in this file lack the "/" at the end and it seems they may imply similar issue. I haven't analysed the code deeply to see if that is a real issue.
>     
>     This bug has been found by running a massive grep-like search using Google's BigQuery on GitHub repositories data. I am also going to work on a CodeQL/Semmle query to be able to find more sophisticated cases like this that can't be found via grepping.
> 
>  tools/perf/util/map.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index a08ca276098e..addd7edb0486 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -89,7 +89,7 @@ static inline bool replace_android_lib(const char *filename, char *newfilename)
>  		return true;
>  	}
>  
> -	if (!strncmp(filename, "/system/lib/", 11)) {
> +	if (!strncmp(filename, "/system/lib/", 12)) {
>  		char *ndk, *app;
>  		const char *arch;
>  		size_t ndk_length;
> -- 
> 2.25.1
> 

-- 

- Arnaldo

Re: [PATCH] Fix off by one in tools/perf strncpy size argument

[Arnaldo Carvalho de Melo]

Em Mon, Mar 09, 2020 at 09:39:40AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Mar 09, 2020 at 11:48:53AM +0100, Dominik 'disconnect3d' Czarnota escreveu:
> > From: disconnect3d <dominik.b.czarnota@gmail.com>
> > 
> > This patch fixes an off-by-one error in strncpy size argument in
> > tools/perf/util/map.c. The issue is that in:
> > 
> >         strncmp(filename, "/system/lib/", 11)
> > 
> > the passed string literal: "/system/lib/" has 12 bytes (without the NULL
> > byte) and the passed size argument is 11. As a result, the logic won't
> > match the ending "/" byte and will pass filepaths that are stored in
> > other directories e.g. "/system/libmalicious/bin" or just
> > "/system/libmalicious".
> > 
> > This functionality seems to be present only on Android. I assume the
> > /system/ directory is only writable by the root user, so I don't
> > think this bug has much (or any) security impact.
> > 
> > Signed-off-by: disconnect3d <dominik.b.czarnota@gmail.com>
> > ---
> > 
> > Notes:
> >     I can't test this patch, so if someone can, please, do so.
> >     
> >     The bug could also be fixed by changing the size argument to `sizeof("string literal")-1` but I am not proposing this change as that would have to be changed in other places.
> 
> So, there are parts of this tools/perf/util/map.c that uses the idiom
> you mention, for instance:
> 
> static inline int is_anon_memory(const char *filename, u32 flags)
> {
>         return flags & MAP_HUGETLB ||
>                !strcmp(filename, "//anon") ||
>                !strncmp(filename, "/dev/zero", sizeof("/dev/zero") - 1) ||
>                !strncmp(filename, "/anon_hugepage", sizeof("/anon_hugepage") - 1);
> }
> 
> So I think we should make all cases use this idim to avoid these
> problems.
> 
> So I'll add your patch, then another, on top, that fixes the other
> off-by-one errors introduced by the android specific code in this patch:

This is the only such off-by-one in that file, and I remembered we have
strstarts(), that we adopted from the kernel sources, so I think its a
better fit, no?

[acme@five linux]$ find . -name "*.c" | grep -v tools/ | xargs grep -w strstarts | wc -l
55
[acme@five linux]$ find tools/ -name "*.c" | xargs grep -w strstarts | wc -l
40
[acme@five linux]$
 
> Fixes: eca818369996 ("perf tools: Add automatic remapping of Android libraries")
> 
> Put this in perf/urgent and then in perf/core move to the more robust
> idiom,
> 
> Thanks,
> 
> - Arnaldo
>      
> >     There are also more cases like this in kernel sources which I am going to report soon.
> >     
> >     Also please note that other path comparisons in this file lack the "/" at the end and it seems they may imply similar issue. I haven't analysed the code deeply to see if that is a real issue.
> >     
> >     This bug has been found by running a massive grep-like search using Google's BigQuery on GitHub repositories data. I am also going to work on a CodeQL/Semmle query to be able to find more sophisticated cases like this that can't be found via grepping.
> > 
> >  tools/perf/util/map.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> > index a08ca276098e..addd7edb0486 100644
> > --- a/tools/perf/util/map.c
> > +++ b/tools/perf/util/map.c
> > @@ -89,7 +89,7 @@ static inline bool replace_android_lib(const char *filename, char *newfilename)
> >  		return true;
> >  	}
> >  
> > -	if (!strncmp(filename, "/system/lib/", 11)) {
> > +	if (!strncmp(filename, "/system/lib/", 12)) {
> >  		char *ndk, *app;
> >  		const char *arch;
> >  		size_t ndk_length;
> > -- 
> > 2.25.1
> > 
> 
> -- 
> 
> - Arnaldo

-- 

- Arnaldo

[tip: perf/urgent] perf map: Fix off by one in strncpy() size argument

[tip-bot2 for disconnect3d]

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     db2c549407d4a76563c579e4768f7d6d32afefba
Gitweb:        https://git.kernel.org/tip/db2c549407d4a76563c579e4768f7d6d32afefba
Author:        disconnect3d <dominik.b.czarnota@gmail.com>
AuthorDate:    Mon, 09 Mar 2020 11:48:53 +01:00
Committer:     Arnaldo Carvalho de Melo <acme@redhat.com>
CommitterDate: Mon, 09 Mar 2020 09:34:45 -03:00

perf map: Fix off by one in strncpy() size argument

This patch fixes an off-by-one error in strncpy size argument in
tools/perf/util/map.c. The issue is that in:

        strncmp(filename, "/system/lib/", 11)

the passed string literal: "/system/lib/" has 12 bytes (without the NULL
byte) and the passed size argument is 11. As a result, the logic won't
match the ending "/" byte and will pass filepaths that are stored in
other directories e.g. "/system/libmalicious/bin" or just
"/system/libmalicious".

This functionality seems to be present only on Android. I assume the
/system/ directory is only writable by the root user, so I don't think
this bug has much (or any) security impact.

Fixes: eca818369996 ("perf tools: Add automatic remapping of Android libraries")
Signed-off-by: disconnect3d <dominik.b.czarnota@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Keeping <john@metanate.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Lentine <mlentine@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200309104855.3775-1-dominik.b.czarnota@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/map.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 9542851..b342f74 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -89,7 +89,7 @@ static inline bool replace_android_lib(const char *filename, char *newfilename)
 		return true;
 	}
 
-	if (!strncmp(filename, "/system/lib/", 11)) {
+	if (!strncmp(filename, "/system/lib/", 12)) {
 		char *ndk, *app;
 		const char *arch;
 		size_t ndk_length;

[tip: perf/core] perf map: Fix off by one in strncpy() size argument

[tip-bot2 for disconnect3d]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     b8fdcfb5a17f1d4fd503caef5c457005a765ecd7
Gitweb:        https://git.kernel.org/tip/b8fdcfb5a17f1d4fd503caef5c457005a765ecd7
Author:        disconnect3d <dominik.b.czarnota@gmail.com>
AuthorDate:    Mon, 09 Mar 2020 11:48:53 +01:00
Committer:     Arnaldo Carvalho de Melo <acme@redhat.com>
CommitterDate: Wed, 11 Mar 2020 10:48:44 -03:00

perf map: Fix off by one in strncpy() size argument

This patch fixes an off-by-one error in strncpy size argument in
tools/perf/util/map.c. The issue is that in:

        strncmp(filename, "/system/lib/", 11)

the passed string literal: "/system/lib/" has 12 bytes (without the NULL
byte) and the passed size argument is 11. As a result, the logic won't
match the ending "/" byte and will pass filepaths that are stored in
other directories e.g. "/system/libmalicious/bin" or just
"/system/libmalicious".

This functionality seems to be present only on Android. I assume the
/system/ directory is only writable by the root user, so I don't think
this bug has much (or any) security impact.

Fixes: eca818369996 ("perf tools: Add automatic remapping of Android libraries")
Signed-off-by: disconnect3d <dominik.b.czarnota@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Keeping <john@metanate.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Lentine <mlentine@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200309104855.3775-1-dominik.b.czarnota@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/map.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 9542851..b342f74 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -89,7 +89,7 @@ static inline bool replace_android_lib(const char *filename, char *newfilename)
 		return true;
 	}
 
-	if (!strncmp(filename, "/system/lib/", 11)) {
+	if (!strncmp(filename, "/system/lib/", 12)) {
 		char *ndk, *app;
 		const char *arch;
 		size_t ndk_length;