From 0ad5c7edda2de25e47077d138d7c371f94590a22 Mon Sep 17 00:00:00 2001 From: Tavian Barnes Date: Wed, 27 Mar 2024 12:41:33 -0400 Subject: xspawn: Don't use posix_spawnp() on macOS On macOS, posix_spawnp() resolves the executable against the $PATH *before* the file_actions are applied, contrary to the upcoming POSIX wording [1] for posix_spawn_file_actions_addfchdir(). [1]: https://www.austingroupbugs.net/view.php?id=1208#c4830 --- src/xspawn.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) (limited to 'src') diff --git a/src/xspawn.c b/src/xspawn.c index dc2bf67..f67adec 100644 --- a/src/xspawn.c +++ b/src/xspawn.c @@ -202,6 +202,18 @@ int bfs_spawn_adddup2(struct bfs_spawn *ctx, int oldfd, int newfd) { return 0; } +/** + * https://www.austingroupbugs.net/view.php?id=1208#c4830 says: + * + * ... a search of the directories passed as the environment variable + * PATH ..., using the working directory of the child process after all + * file_actions have been performed. + * + * but macOS resolves the PATH *before* file_actions (because there + * posix_spawn() is its own syscall). + */ +#define BFS_POSIX_SPAWNP_AFTER_FCHDIR !__APPLE__ + int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) { struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_FCHDIR); if (!action) { @@ -452,12 +464,15 @@ static int bfs_resolve_early(struct bfs_resolver *res, const char *exe, const st } bool can_finish = bfs_can_resolve_early(res, ctx); + +#if BFS_POSIX_SPAWNP_AFTER_FCHDIR bool use_posix = ctx && (ctx->flags & BFS_SPAWN_USE_POSIX); if (!can_finish && use_posix) { // posix_spawnp() will do the resolution, so don't bother // allocating a buffer return 0; } +#endif res->len = bfs_resolve_capacity(res); res->buf = malloc(res->len); @@ -477,6 +492,7 @@ fail: } #if _POSIX_SPAWN > 0 + /** bfs_spawn() implementation using posix_spawn(). */ static pid_t bfs_posix_spawn(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp) { pid_t ret; @@ -493,8 +509,24 @@ static pid_t bfs_posix_spawn(struct bfs_resolver *res, const struct bfs_spawn *c return ret; } + +/** Check if we can use posix_spawn(). */ +static bool bfs_use_posix_spawn(const struct bfs_resolver *res, const struct bfs_spawn *ctx) { + if (!(ctx->flags & BFS_SPAWN_USE_POSIX)) { + return false; + } + +#if !BFS_POSIX_SPAWNP_AFTER_FCHDIR + if (!res->done) { + return false; + } #endif + return true; +} + +#endif // _POSIX_SPAWN > 0 + /** Actually exec() the new process. */ static noreturn void bfs_spawn_exec(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp, int pipefd[2]) { xclose(pipefd[0]); @@ -607,7 +639,7 @@ static pid_t bfs_fork_spawn(struct bfs_resolver *res, const struct bfs_spawn *ct /** Call the right bfs_spawn() implementation. */ static pid_t bfs_spawn_impl(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp) { #if _POSIX_SPAWN > 0 - if (ctx->flags & BFS_SPAWN_USE_POSIX) { + if (bfs_use_posix_spawn(res, ctx)) { return bfs_posix_spawn(res, ctx, argv, envp); } #endif -- cgit v1.2.3