From 36f4af05680d0f8f67b870bf72241d7d2fefd91b Mon Sep 17 00:00:00 2001 From: Maanya Goenka Date: Wed, 4 Aug 2021 11:59:45 -0700 Subject: [PATCH] path-util: teach find_executable_full how to look into the root directory When the root parameter in find_executable_full is set, chase_symlinks prefixes this root to every check of the path name to find the complete path of the execuatble in case the path provided is not absolute. This is only done for the non NULL root because otherwise the chase_symlinks function would alter the behavior of some of the callers which would in turn alter the outputs in a way that is undesirable. The find_execuatble_full function is invoked by the verify_executable function in analyze-verify. --- src/analyze/analyze-verify.c | 2 +- src/basic/path-util.c | 38 +++++++++++++++++++++++++++++++++++- src/basic/path-util.h | 4 ++-- src/core/execute.c | 2 +- src/test/test-path-util.c | 10 +++++----- 5 files changed, 46 insertions(+), 10 deletions(-) diff --git a/src/analyze/analyze-verify.c b/src/analyze/analyze-verify.c index 4fcec2fcdc..99bce68ca4 100644 --- a/src/analyze/analyze-verify.c +++ b/src/analyze/analyze-verify.c @@ -124,7 +124,7 @@ int verify_executable(Unit *u, const ExecCommand *exec) { if (exec->flags & EXEC_COMMAND_IGNORE_FAILURE) return 0; - r = find_executable_full(exec->path, false, NULL, NULL); + r = find_executable_full(exec->path, /* root= */ NULL, false, NULL, NULL); if (r < 0) return log_unit_error_errno(u, r, "Command %s is not executable: %m", exec->path); diff --git a/src/basic/path-util.c b/src/basic/path-util.c index 4aebb6541e..fe799da20b 100644 --- a/src/basic/path-util.c +++ b/src/basic/path-util.c @@ -639,7 +639,7 @@ static int check_x_access(const char *path, int *ret_fd) { return 0; } -int find_executable_full(const char *name, bool use_path_envvar, char **ret_filename, int *ret_fd) { +int find_executable_full(const char *name, const char *root, bool use_path_envvar, char **ret_filename, int *ret_fd) { int last_error, r; const char *p = NULL; @@ -647,6 +647,25 @@ int find_executable_full(const char *name, bool use_path_envvar, char **ret_file if (is_path(name)) { _cleanup_close_ int fd = -1; + _cleanup_free_ char *path_name = NULL; + + /* Function chase_symlinks() is invoked only when root is not NULL, + * as using it regardless of root value would alter the behavior + * of existing callers for example: /bin/sleep would become + * /usr/bin/sleep when find_executables is called. Hence, this function + * should be invoked when needed to avoid unforeseen regression or other + * complicated changes. */ + if (root) { + r = chase_symlinks(name, + root, + CHASE_PREFIX_ROOT, + &path_name, + /* ret_fd= */ NULL); /* prefix root to name in case full paths are not specified */ + if (r < 0) + return r; + + name = path_name; + } r = check_x_access(name, ret_fd ? &fd : NULL); if (r < 0) @@ -690,6 +709,23 @@ int find_executable_full(const char *name, bool use_path_envvar, char **ret_file if (!path_extend(&element, name)) return -ENOMEM; + if (root) { + char *path_name; + + r = chase_symlinks(element, + root, + CHASE_PREFIX_ROOT, + &path_name, + /* ret_fd= */ NULL); + if (r < 0) { + if (r != -EACCES) + last_error = r; + continue; + } + + free_and_replace(element, path_name); + } + r = check_x_access(element, ret_fd ? &fd : NULL); if (r < 0) { /* PATH entries which we don't have access to are ignored, as per tradition. */ diff --git a/src/basic/path-util.h b/src/basic/path-util.h index 26e7362d1f..0d69145497 100644 --- a/src/basic/path-util.h +++ b/src/basic/path-util.h @@ -99,9 +99,9 @@ int path_strv_make_absolute_cwd(char **l); char** path_strv_resolve(char **l, const char *root); char** path_strv_resolve_uniq(char **l, const char *root); -int find_executable_full(const char *name, bool use_path_envvar, char **ret_filename, int *ret_fd); +int find_executable_full(const char *name, const char *root, bool use_path_envvar, char **ret_filename, int *ret_fd); static inline int find_executable(const char *name, char **ret_filename) { - return find_executable_full(name, true, ret_filename, NULL); + return find_executable_full(name, /* root= */ NULL, true, ret_filename, NULL); } bool paths_check_timestamp(const char* const* paths, usec_t *paths_ts_usec, bool update); diff --git a/src/core/execute.c b/src/core/execute.c index 4608956259..6635a35abf 100644 --- a/src/core/execute.c +++ b/src/core/execute.c @@ -4351,7 +4351,7 @@ static int exec_child( _cleanup_free_ char *executable = NULL; _cleanup_close_ int executable_fd = -1; - r = find_executable_full(command->path, false, &executable, &executable_fd); + r = find_executable_full(command->path, /* root= */ NULL, false, &executable, &executable_fd); if (r < 0) { if (r != -ENOMEM && (command->flags & EXEC_COMMAND_IGNORE_FAILURE)) { log_unit_struct_errno(unit, LOG_INFO, r, diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c index ceea7a62f5..1a0fda5d1a 100644 --- a/src/test/test-path-util.c +++ b/src/test/test-path-util.c @@ -204,12 +204,12 @@ static void test_find_executable_full(void) { log_info("/* %s */", __func__); - assert_se(find_executable_full("sh", true, &p, NULL) == 0); + assert_se(find_executable_full("sh", NULL, true, &p, NULL) == 0); puts(p); assert_se(streq(basename(p), "sh")); free(p); - assert_se(find_executable_full("sh", false, &p, NULL) == 0); + assert_se(find_executable_full("sh", NULL, false, &p, NULL) == 0); puts(p); assert_se(streq(basename(p), "sh")); free(p); @@ -221,12 +221,12 @@ static void test_find_executable_full(void) { assert_se(unsetenv("PATH") == 0); - assert_se(find_executable_full("sh", true, &p, NULL) == 0); + assert_se(find_executable_full("sh", NULL, true, &p, NULL) == 0); puts(p); assert_se(streq(basename(p), "sh")); free(p); - assert_se(find_executable_full("sh", false, &p, NULL) == 0); + assert_se(find_executable_full("sh", NULL, false, &p, NULL) == 0); puts(p); assert_se(streq(basename(p), "sh")); free(p); @@ -277,7 +277,7 @@ static void test_find_executable_exec_one(const char *path) { pid_t pid; int r; - r = find_executable_full(path, false, &t, &fd); + r = find_executable_full(path, NULL, false, &t, &fd); log_info_errno(r, "%s: %s → %s: %d/%m", __func__, path, t ?: "-", fd);