From f83bb9b8e97656ae0d3e2a31e859363e2d4d5832 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Fri, 29 Jan 2016 11:43:40 -0200 Subject: posix: Remove dynamic memory allocation from execl{e,p} GLIBC execl{e,p} implementation might use malloc if the total number of arguments exceed initial assumption size (1024). This might lead to issues in two situations: 1. execl/execle is stated to be async-signal-safe by POSIX [1]. However if execl is used in a signal handler with a large argument set (that may call malloc internally) and if the resulting call fails it might lead malloc in the program in a bad state. 2. If the functions are used in a vfork/clone(VFORK) situation it also might issue malloc internal bad state. This patch fixes it by using stack allocation instead. It also fixes BZ#19534. Tested on x86_64. [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html [BZ #19534] * posix/execl.c (execl): Remove dynamic memory allocation. * posix/execle.c (execle): Likewise. * posix/execlp.c (execlp): Likewise. --- posix/execle.c | 70 +++++++++++++++++++++++----------------------------------- 1 file changed, 28 insertions(+), 42 deletions(-) (limited to 'posix/execle.c') diff --git a/posix/execle.c b/posix/execle.c index 8edc03a84a..50e843e7d7 100644 --- a/posix/execle.c +++ b/posix/execle.c @@ -17,57 +17,43 @@ #include #include -#include -#include -#include - -#include +#include +#include /* Execute PATH with all arguments after PATH until a NULL pointer, and the argument after that for environment. */ int execle (const char *path, const char *arg, ...) { -#define INITIAL_ARGV_MAX 1024 - size_t argv_max = INITIAL_ARGV_MAX; - const char *initial_argv[INITIAL_ARGV_MAX]; - const char **argv = initial_argv; - va_list args; - argv[0] = arg; - - va_start (args, arg); - unsigned int i = 0; - while (argv[i++] != NULL) + ptrdiff_t argc; + va_list ap; + va_start (ap, arg); + for (argc = 1; va_arg (ap, const char *); argc++) { - if (i == argv_max) + if (argc == INT_MAX) { - argv_max *= 2; - const char **nptr = realloc (argv == initial_argv ? NULL : argv, - argv_max * sizeof (const char *)); - if (nptr == NULL) - { - if (argv != initial_argv) - free (argv); - va_end (args); - return -1; - } - if (argv == initial_argv) - /* We have to copy the already filled-in data ourselves. */ - memcpy (nptr, argv, i * sizeof (const char *)); - - argv = nptr; + va_end (ap); + errno = E2BIG; + return -1; } - - argv[i] = va_arg (args, const char *); } - - const char *const *envp = va_arg (args, const char *const *); - va_end (args); - - int ret = __execve (path, (char *const *) argv, (char *const *) envp); - if (argv != initial_argv) - free (argv); - - return ret; + va_end (ap); + + /* Avoid dynamic memory allocation due two main issues: + 1. The function should be async-signal-safe and a running on a signal + handler with a fail outcome might lead to malloc bad state. + 2. It might be used in a vfork/clone(VFORK) scenario where using + malloc also might lead to internal bad state. */ + ptrdiff_t i; + char *argv[argc + 1]; + char **envp; + va_start (ap, arg); + argv[0] = (char *) arg; + for (i = 1; i <= argc; i++) + argv[i] = va_arg (ap, char *); + envp = va_arg (ap, char **); + va_end (ap); + + return __execve (path, argv, envp); } libc_hidden_def (execle) -- cgit v1.2.3