From 91fe8b8a5cb47b44dcaf72c9760f1bda001c011b Mon Sep 17 00:00:00 2001 From: Martin Pitt Date: Tue, 9 Jun 2015 16:16:56 +0200 Subject: [PATCH] path-util: Fix path_is_mount_point for parent mount points in symlink mode When we have a structure like this: /bin -> /usr/bin /usr is a mount point Then path_is_mount_point("/bin", AT_SYMLINK_FOLLOW) needs to look at the pair /usr/bin and /usr, not at the pair / and /usr/bin, as the latter have different mount IDs. But we only want to consider the base name, not any parent. Thus we have to resolve the given path first to get the real parent when allowing symlinks. Bug: https://github.com/systemd/systemd/issues/61 --- src/shared/path-util.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/src/shared/path-util.c b/src/shared/path-util.c index be50a1865..537705446 100644 --- a/src/shared/path-util.c +++ b/src/shared/path-util.c @@ -640,7 +640,7 @@ fallback_fstat: /* flags can be AT_SYMLINK_FOLLOW or 0 */ int path_is_mount_point(const char *t, int flags) { _cleanup_close_ int fd = -1; - _cleanup_free_ char *parent = NULL; + _cleanup_free_ char *canonical = NULL, *parent = NULL; int r; assert(t); @@ -648,7 +648,17 @@ int path_is_mount_point(const char *t, int flags) { if (path_equal(t, "/")) return 1; - r = path_get_parent(t, &parent); + /* we need to resolve symlinks manually, we can't just rely on + * fd_is_mount_point() to do that for us; if we have a structure like + * /bin -> /usr/bin/ and /usr is a mount point, then the parent that we + * look at needs to be /usr, not /. */ + if (flags & AT_SYMLINK_FOLLOW) { + canonical = canonicalize_file_name(t); + if (!canonical) + return -errno; + } + + r = path_get_parent(canonical ?: t, &parent); if (r < 0) return r; @@ -656,7 +666,7 @@ int path_is_mount_point(const char *t, int flags) { if (fd < 0) return -errno; - return fd_is_mount_point(fd, basename(t), flags); + return fd_is_mount_point(fd, basename(canonical ?: t), flags); } int path_is_read_only_fs(const char *path) { -- 2.30.2