linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Kees Cook <keescook@chromium.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: "Kees Cook" <keescook@chromium.org>,
	"Valdis Klētnieks" <valdis.kletnieks@vt.edu>,
	"Arnaldo Carvalho de Melo" <acme@redhat.com>,
	"Justin Forbes" <jmforbes@linuxtx.org>,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH v2] tools: Fix use-after-free for realloc(..., 0)
Date: Sun, 13 Feb 2022 10:24:43 -0800	[thread overview]
Message-ID: <20220213182443.4037039-1-keescook@chromium.org> (raw)

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


             reply	other threads:[~2022-02-13 18:24 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-13 18:24 Kees Cook [this message]
2022-02-14 20:07 ` [PATCH v2] tools: Fix use-after-free for realloc(..., 0) Josh Poimboeuf
2022-02-15 20:42   ` Arnaldo Carvalho de Melo
2022-02-15 22:14     ` Josh Poimboeuf
2022-02-15 20:58 ` Justin Forbes

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20220213182443.4037039-1-keescook@chromium.org \
    --to=keescook@chromium.org \
    --cc=acme@redhat.com \
    --cc=jmforbes@linuxtx.org \
    --cc=jpoimboe@redhat.com \
    --cc=linux-hardening@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=valdis.kletnieks@vt.edu \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).