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[PATCH v2] tools: Fix use-after-free for realloc(..., 0)

Kees Cook posted 1 patch 4 years, 4 months ago
Failed in applying to current master (apply log)
tools/lib/subcmd/subcmd-util.h | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)
[PATCH v2] tools: Fix use-after-free for realloc(..., 0)
Posted by Kees Cook 4 years, 4 months ago 
GCC 12 was correctly reporting a potential use-after-free condition in
the xrealloc helper. Fix the warning by avoiding an implicit "free(ptr)"
when size == 0:

In file included from help.c:12:
In function 'xrealloc',
    inlined from 'add_cmdname' at help.c:24:2: subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
   56 |                 ret = realloc(ptr, size);
      |                       ^~~~~~~~~~~~~~~~~~
subcmd-util.h:52:21: note: call to 'realloc' here
   52 |         void *ret = realloc(ptr, size);
      |                     ^~~~~~~~~~~~~~~~~~
subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
   58 |                         ret = realloc(ptr, 1);
      |                               ^~~~~~~~~~~~~~~
subcmd-util.h:52:21: note: call to 'realloc' here
   52 |         void *ret = realloc(ptr, size);
      |                     ^~~~~~~~~~~~~~~~~~

Reported-by: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
Fixes: 2f4ce5ec1d44 ("perf tools: Finalize subcmd independence")
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v1: https://lore.kernel.org/lkml/20220212181855.3460176-1-keescook@chromium.org/
v2: simplify logic (josh)
---
 tools/lib/subcmd/subcmd-util.h | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/tools/lib/subcmd/subcmd-util.h b/tools/lib/subcmd/subcmd-util.h
index 794a375dad36..b2aec04fce8f 100644
--- a/tools/lib/subcmd/subcmd-util.h
+++ b/tools/lib/subcmd/subcmd-util.h
@@ -50,15 +50,8 @@ static NORETURN inline void die(const char *err, ...)
 static inline void *xrealloc(void *ptr, size_t size)
 {
 	void *ret = realloc(ptr, size);
-	if (!ret && !size)
-		ret = realloc(ptr, 1);
-	if (!ret) {
-		ret = realloc(ptr, size);
-		if (!ret && !size)
-			ret = realloc(ptr, 1);
-		if (!ret)
-			die("Out of memory, realloc failed");
-	}
+	if (!ret)
+		die("Out of memory, realloc failed");
 	return ret;
 }
 
-- 
2.30.2
Re: [PATCH v2] tools: Fix use-after-free for realloc(..., 0)
Posted by Justin Forbes 4 years, 4 months ago 
On Sun, Feb 13, 2022 at 10:24:43AM -0800, Kees Cook wrote:
> GCC 12 was correctly reporting a potential use-after-free condition in
> the xrealloc helper. Fix the warning by avoiding an implicit "free(ptr)"
> when size == 0:
> 
> In file included from help.c:12:
> In function 'xrealloc',
>     inlined from 'add_cmdname' at help.c:24:2: subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
>    56 |                 ret = realloc(ptr, size);
>       |                       ^~~~~~~~~~~~~~~~~~
> subcmd-util.h:52:21: note: call to 'realloc' here
>    52 |         void *ret = realloc(ptr, size);
>       |                     ^~~~~~~~~~~~~~~~~~
> subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
>    58 |                         ret = realloc(ptr, 1);
>       |                               ^~~~~~~~~~~~~~~
> subcmd-util.h:52:21: note: call to 'realloc' here
>    52 |         void *ret = realloc(ptr, size);
>       |                     ^~~~~~~~~~~~~~~~~~
> 
> Reported-by: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
> Fixes: 2f4ce5ec1d44 ("perf tools: Finalize subcmd independence")
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Tested this patch with the Fedora rawhide builds, and this does indeed
fix the issue.

Tested-by: Justin M. Forbes <jforbes@fedoraproject.org>
Re: [PATCH v2] tools: Fix use-after-free for realloc(..., 0)
Posted by Josh Poimboeuf 4 years, 4 months ago 
On Sun, Feb 13, 2022 at 10:24:43AM -0800, Kees Cook wrote:
> GCC 12 was correctly reporting a potential use-after-free condition in
> the xrealloc helper. Fix the warning by avoiding an implicit "free(ptr)"
> when size == 0:
> 
> In file included from help.c:12:
> In function 'xrealloc',
>     inlined from 'add_cmdname' at help.c:24:2: subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
>    56 |                 ret = realloc(ptr, size);
>       |                       ^~~~~~~~~~~~~~~~~~
> subcmd-util.h:52:21: note: call to 'realloc' here
>    52 |         void *ret = realloc(ptr, size);
>       |                     ^~~~~~~~~~~~~~~~~~
> subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
>    58 |                         ret = realloc(ptr, 1);
>       |                               ^~~~~~~~~~~~~~~
> subcmd-util.h:52:21: note: call to 'realloc' here
>    52 |         void *ret = realloc(ptr, size);
>       |                     ^~~~~~~~~~~~~~~~~~
> 
> Reported-by: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
> Fixes: 2f4ce5ec1d44 ("perf tools: Finalize subcmd independence")
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v1: https://lore.kernel.org/lkml/20220212181855.3460176-1-keescook@chromium.org/
> v2: simplify logic (josh)

Thanks, running through testing now.

-- 
Josh
Re: [PATCH v2] tools: Fix use-after-free for realloc(..., 0)
Posted by Arnaldo Carvalho de Melo 4 years, 4 months ago 
Em Mon, Feb 14, 2022 at 12:07:30PM -0800, Josh Poimboeuf escreveu:
> On Sun, Feb 13, 2022 at 10:24:43AM -0800, Kees Cook wrote:
> > GCC 12 was correctly reporting a potential use-after-free condition in
> > the xrealloc helper. Fix the warning by avoiding an implicit "free(ptr)"
> > when size == 0:
> > 
> > In file included from help.c:12:
> > In function 'xrealloc',
> >     inlined from 'add_cmdname' at help.c:24:2: subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
> >    56 |                 ret = realloc(ptr, size);
> >       |                       ^~~~~~~~~~~~~~~~~~
> > subcmd-util.h:52:21: note: call to 'realloc' here
> >    52 |         void *ret = realloc(ptr, size);
> >       |                     ^~~~~~~~~~~~~~~~~~
> > subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
> >    58 |                         ret = realloc(ptr, 1);
> >       |                               ^~~~~~~~~~~~~~~
> > subcmd-util.h:52:21: note: call to 'realloc' here
> >    52 |         void *ret = realloc(ptr, size);
> >       |                     ^~~~~~~~~~~~~~~~~~
> > 
> > Reported-by: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
> > Fixes: 2f4ce5ec1d44 ("perf tools: Finalize subcmd independence")
> > Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > v1: https://lore.kernel.org/lkml/20220212181855.3460176-1-keescook@chromium.org/
> > v2: simplify logic (josh)
> 
> Thanks, running through testing now.

I assume that testing went ok, may I add a Tested-by: you?

- Arnaldo
Re: [PATCH v2] tools: Fix use-after-free for realloc(..., 0)
Posted by Josh Poimboeuf 4 years, 4 months ago 
On Tue, Feb 15, 2022 at 05:42:35PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, Feb 14, 2022 at 12:07:30PM -0800, Josh Poimboeuf escreveu:
> > On Sun, Feb 13, 2022 at 10:24:43AM -0800, Kees Cook wrote:
> > > GCC 12 was correctly reporting a potential use-after-free condition in
> > > the xrealloc helper. Fix the warning by avoiding an implicit "free(ptr)"
> > > when size == 0:
> > > 
> > > In file included from help.c:12:
> > > In function 'xrealloc',
> > >     inlined from 'add_cmdname' at help.c:24:2: subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
> > >    56 |                 ret = realloc(ptr, size);
> > >       |                       ^~~~~~~~~~~~~~~~~~
> > > subcmd-util.h:52:21: note: call to 'realloc' here
> > >    52 |         void *ret = realloc(ptr, size);
> > >       |                     ^~~~~~~~~~~~~~~~~~
> > > subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
> > >    58 |                         ret = realloc(ptr, 1);
> > >       |                               ^~~~~~~~~~~~~~~
> > > subcmd-util.h:52:21: note: call to 'realloc' here
> > >    52 |         void *ret = realloc(ptr, size);
> > >       |                     ^~~~~~~~~~~~~~~~~~
> > > 
> > > Reported-by: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
> > > Fixes: 2f4ce5ec1d44 ("perf tools: Finalize subcmd independence")
> > > Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > ---
> > > v1: https://lore.kernel.org/lkml/20220212181855.3460176-1-keescook@chromium.org/
> > > v2: simplify logic (josh)
> > 
> > Thanks, running through testing now.
> 
> I assume that testing went ok, may I add a Tested-by: you?

Yes, feel free to add:

Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>

-- 
Josh

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