diff options
Diffstat (limited to 'src/xspawn.c')
| -rw-r--r-- | src/xspawn.c | 199 |
1 files changed, 154 insertions, 45 deletions
diff --git a/src/xspawn.c b/src/xspawn.c index 0b0cea4..ee62c05 100644 --- a/src/xspawn.c +++ b/src/xspawn.c @@ -1,24 +1,29 @@ // Copyright © Tavian Barnes <tavianator@tavianator.com> // SPDX-License-Identifier: 0BSD -#include "prelude.h" #include "xspawn.h" + #include "alloc.h" +#include "bfs.h" #include "bfstd.h" +#include "diag.h" #include "list.h" +#include "sighook.h" + #include <errno.h> #include <fcntl.h> +#include <signal.h> #include <stdlib.h> #include <string.h> #include <sys/resource.h> #include <sys/types.h> #include <unistd.h> -#if BFS_USE_PATHS_H +#if __has_include(<paths.h>) # include <paths.h> #endif -#if _POSIX_SPAWN > 0 +#if BFS_POSIX_SPAWN >= 0 # include <spawn.h> #endif @@ -68,29 +73,42 @@ int bfs_spawn_init(struct bfs_spawn *ctx) { ctx->flags = 0; SLIST_INIT(ctx); -#if _POSIX_SPAWN > 0 - ctx->flags |= BFS_SPAWN_USE_POSIX; +#if BFS_POSIX_SPAWN >= 0 + if (sysoption(SPAWN) > 0) { + ctx->flags |= BFS_SPAWN_USE_POSIX; - errno = posix_spawn_file_actions_init(&ctx->actions); - if (errno != 0) { - return -1; - } + errno = posix_spawn_file_actions_init(&ctx->actions); + if (errno != 0) { + return -1; + } - errno = posix_spawnattr_init(&ctx->attr); - if (errno != 0) { - posix_spawn_file_actions_destroy(&ctx->actions); - return -1; + errno = posix_spawnattr_init(&ctx->attr); + if (errno != 0) { + posix_spawn_file_actions_destroy(&ctx->actions); + return -1; + } } #endif return 0; } -int bfs_spawn_destroy(struct bfs_spawn *ctx) { -#if _POSIX_SPAWN > 0 - posix_spawnattr_destroy(&ctx->attr); - posix_spawn_file_actions_destroy(&ctx->actions); +/** + * Clear the BFS_SPAWN_USE_POSIX flag and free the attributes. + */ +static void bfs_spawn_clear_posix(struct bfs_spawn *ctx) { + if (ctx->flags & BFS_SPAWN_USE_POSIX) { + ctx->flags &= ~BFS_SPAWN_USE_POSIX; + +#if BFS_POSIX_SPAWN >= 0 + posix_spawnattr_destroy(&ctx->attr); + posix_spawn_file_actions_destroy(&ctx->actions); #endif + } +} + +int bfs_spawn_destroy(struct bfs_spawn *ctx) { + bfs_spawn_clear_posix(ctx); for_slist (struct bfs_spawn_action, action, ctx) { free(action); @@ -99,9 +117,9 @@ int bfs_spawn_destroy(struct bfs_spawn *ctx) { return 0; } -#if _POSIX_SPAWN > 0 +#if BFS_POSIX_SPAWN >= 0 /** Set some posix_spawnattr flags. */ -attr(maybe_unused) +_maybe_unused static int bfs_spawn_addflags(struct bfs_spawn *ctx, short flags) { short prev; errno = posix_spawnattr_getflags(&ctx->attr, &prev); @@ -119,7 +137,7 @@ static int bfs_spawn_addflags(struct bfs_spawn *ctx, short flags) { return 0; } -#endif // _POSIX_SPAWN > 0 +#endif /** Allocate a spawn action. */ static struct bfs_spawn_action *bfs_spawn_action(enum bfs_spawn_op op) { @@ -141,7 +159,7 @@ int bfs_spawn_addopen(struct bfs_spawn *ctx, int fd, const char *path, int flags return -1; } -#if _POSIX_SPAWN > 0 +#if BFS_POSIX_SPAWN >= 0 if (ctx->flags & BFS_SPAWN_USE_POSIX) { errno = posix_spawn_file_actions_addopen(&ctx->actions, fd, path, flags, mode); if (errno != 0) { @@ -165,7 +183,7 @@ int bfs_spawn_addclose(struct bfs_spawn *ctx, int fd) { return -1; } -#if _POSIX_SPAWN > 0 +#if BFS_POSIX_SPAWN >= 0 if (ctx->flags & BFS_SPAWN_USE_POSIX) { errno = posix_spawn_file_actions_addclose(&ctx->actions, fd); if (errno != 0) { @@ -186,7 +204,7 @@ int bfs_spawn_adddup2(struct bfs_spawn *ctx, int oldfd, int newfd) { return -1; } -#if _POSIX_SPAWN > 0 +#if BFS_POSIX_SPAWN >= 0 if (ctx->flags & BFS_SPAWN_USE_POSIX) { errno = posix_spawn_file_actions_adddup2(&ctx->actions, oldfd, newfd); if (errno != 0) { @@ -214,19 +232,35 @@ int bfs_spawn_adddup2(struct bfs_spawn *ctx, int oldfd, int newfd) { */ #define BFS_POSIX_SPAWNP_AFTER_FCHDIR !(__APPLE__ || __NetBSD__) +/** + * NetBSD even resolves the executable before file actions with posix_spawn()! + */ +#define BFS_POSIX_SPAWN_AFTER_FCHDIR !__NetBSD__ + int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) { struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_FCHDIR); if (!action) { return -1; } +#if __APPLE__ + // macOS has a bug that causes EBADF when an fchdir() action refers to a + // file opened by the file actions + for_slist (struct bfs_spawn_action, prev, ctx) { + if (fd == prev->out_fd) { + bfs_spawn_clear_posix(ctx); + break; + } + } +#endif + #if BFS_HAS_POSIX_SPAWN_ADDFCHDIR # define BFS_POSIX_SPAWN_ADDFCHDIR posix_spawn_file_actions_addfchdir #elif BFS_HAS_POSIX_SPAWN_ADDFCHDIR_NP # define BFS_POSIX_SPAWN_ADDFCHDIR posix_spawn_file_actions_addfchdir_np #endif -#if _POSIX_SPAWN > 0 && defined(BFS_POSIX_SPAWN_FCHDIR) +#if BFS_POSIX_SPAWN >= 0 && defined(BFS_POSIX_SPAWN_ADDFCHDIR) if (ctx->flags & BFS_SPAWN_USE_POSIX) { errno = BFS_POSIX_SPAWN_ADDFCHDIR(&ctx->actions, fd); if (errno != 0) { @@ -235,7 +269,7 @@ int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) { } } #else - ctx->flags &= ~BFS_SPAWN_USE_POSIX; + bfs_spawn_clear_posix(ctx); #endif action->in_fd = fd; @@ -259,7 +293,7 @@ int bfs_spawn_setrlimit(struct bfs_spawn *ctx, int resource, const struct rlimit goto fail; } #else - ctx->flags &= ~BFS_SPAWN_USE_POSIX; + bfs_spawn_clear_posix(ctx); #endif action->resource = resource; @@ -383,18 +417,40 @@ static bool bfs_resolve_relative(const struct bfs_resolver *res) { return false; } +/** Check if the actions include fchdir(). */ +static bool bfs_spawn_will_chdir(const struct bfs_spawn *ctx) { + if (ctx) { + for_slist (const struct bfs_spawn_action, action, ctx) { + if (action->op == BFS_SPAWN_FCHDIR) { + return true; + } + } + } + + return false; +} + +/** Check if we can call xfaccessat() before file actions. */ +static bool bfs_can_access_early(const struct bfs_resolver *res, const struct bfs_spawn *ctx) { + if (res->exe[0] == '/') { + return true; + } + + if (bfs_spawn_will_chdir(ctx)) { + return false; + } + + return true; +} + /** Check if we can resolve the executable before file actions. */ static bool bfs_can_resolve_early(const struct bfs_resolver *res, const struct bfs_spawn *ctx) { if (!bfs_resolve_relative(res)) { return true; } - if (ctx) { - for_slist (const struct bfs_spawn_action, action, ctx) { - if (action->op == BFS_SPAWN_FCHDIR) { - return false; - } - } + if (bfs_spawn_will_chdir(ctx)) { + return false; } return true; @@ -424,6 +480,17 @@ static int bfs_resolve_early(struct bfs_resolver *res, const char *exe, const st }; if (bfs_can_skip_resolve(res, ctx)) { + if (bfs_can_access_early(res, ctx)) { + // Do this check eagerly, even though posix_spawn()/execv() also + // would, because: + // + // - faccessat() is faster than fork()/clone() + execv() + // - posix_spawn() is not guaranteed to report ENOENT + if (xfaccessat(AT_FDCWD, exe, X_OK) != 0) { + return -1; + } + } + res->done = true; return 0; } @@ -471,7 +538,7 @@ fail: return -1; } -#if _POSIX_SPAWN > 0 +#if BFS_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) { @@ -502,13 +569,20 @@ static bool bfs_use_posix_spawn(const struct bfs_resolver *res, const struct bfs } #endif +#if !BFS_POSIX_SPAWN_AFTER_FCHDIR + if (res->exe[0] != '/' && bfs_spawn_will_chdir(ctx)) { + return false; + } +#endif + return true; } -#endif // _POSIX_SPAWN > 0 +#endif // BFS_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]) { +_noreturn +static void bfs_spawn_exec(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp, const sigset_t *mask, int pipefd[2]) { xclose(pipefd[0]); for_slist (const struct bfs_spawn_action, action, ctx) { @@ -569,6 +643,18 @@ static noreturn void bfs_spawn_exec(struct bfs_resolver *res, const struct bfs_s goto fail; } + // Reset signal handlers to their original values before we unblock + // signals, so that handlers don't run in both the parent and the child + if (sigreset() != 0) { + goto fail; + } + + // Restore the original signal mask for the child process + errno = pthread_sigmask(SIG_SETMASK, mask, NULL); + if (errno != 0) { + goto fail; + } + execve(res->exe, argv, envp); fail:; @@ -590,35 +676,58 @@ static pid_t bfs_fork_spawn(struct bfs_resolver *res, const struct bfs_spawn *ct return -1; } + // Block signals before fork() so handlers don't run in the child + sigset_t new_mask; + if (sigfillset(&new_mask) != 0) { + goto fail; + } + sigset_t old_mask; + errno = pthread_sigmask(SIG_BLOCK, &new_mask, &old_mask); + if (errno != 0) { + goto fail; + } + +#if BFS_HAS__FORK + pid_t pid = _Fork(); +#else pid_t pid = fork(); - if (pid < 0) { - close_quietly(pipefd[1]); - close_quietly(pipefd[0]); - return -1; - } else if (pid == 0) { +#endif + if (pid == 0) { // Child - bfs_spawn_exec(res, ctx, argv, envp, pipefd); + bfs_spawn_exec(res, ctx, argv, envp, &old_mask, pipefd); + } + + // Restore the original signal mask + errno = pthread_sigmask(SIG_SETMASK, &old_mask, NULL); + bfs_everify(errno == 0, "pthread_sigmask()"); + + if (pid < 0) { + // fork() failed + goto fail; } - // Parent xclose(pipefd[1]); int error; ssize_t nbytes = xread(pipefd[0], &error, sizeof(error)); xclose(pipefd[0]); if (nbytes == sizeof(error)) { - int wstatus; - xwaitpid(pid, &wstatus, 0); + xwaitpid(pid, NULL, 0); errno = error; return -1; } return pid; + +fail: + close_quietly(pipefd[1]); + close_quietly(pipefd[0]); + return -1; } /** 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 BFS_POSIX_SPAWN >= 0 if (bfs_use_posix_spawn(res, ctx)) { return bfs_posix_spawn(res, ctx, argv, envp); } |