lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Sat, 12 Feb 2022 10:18:55 -0800 From: Kees Cook <keescook@...omium.org> To: Josh Poimboeuf <jpoimboe@...hat.com> Cc: Kees Cook <keescook@...omium.org>, Valdis Klētnieks <valdis.kletnieks@...edu>, Justin Forbes <jmforbes@...uxtx.org>, Arnaldo Carvalho de Melo <acme@...hat.com>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: [PATCH] tools: Fix use-after-free for realloc(..., 0) 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@...edu> Fixes: 2f4ce5ec1d44 ("perf tools: Finalize subcmd independence") Cc: Josh Poimboeuf <jpoimboe@...hat.com> Signed-off-by: Kees Cook <keescook@...omium.org> --- tools/lib/subcmd/subcmd-util.h | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/tools/lib/subcmd/subcmd-util.h b/tools/lib/subcmd/subcmd-util.h index 794a375dad36..de392fc5fd3a 100644 --- a/tools/lib/subcmd/subcmd-util.h +++ b/tools/lib/subcmd/subcmd-util.h @@ -49,15 +49,24 @@ 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); + void *ret; + + /* + * Convert a zero-sized allocation into 1 byte, since + * realloc(ptr, 0) means free(ptr), but we don't want + * to release the memory. For a new allocation (when + * ptr == NULL), avoid triggering NULL-checking error + * conditions for zero-sized allocations. + */ + if (!size) + size = 1; + ret = realloc(ptr, size); if (!ret) { - ret = realloc(ptr, size); - if (!ret && !size) - ret = realloc(ptr, 1); - if (!ret) - die("Out of memory, realloc failed"); + /* + * If realloc() fails, the original block is left untouched; + * it is not freed or moved. + */ + die("Out of memory, realloc failed"); } return ret; } -- 2.30.2
Powered by blists - more mailing lists