| From 5d4c6b2f4b88b69b31f967371d2a6136c65dc3fd Mon Sep 17 00:00:00 2001 |
| From: Andre McCurdy <armccurdy@gmail.com> |
| Date: Tue, 10 Oct 2017 14:33:30 -0700 |
| Subject: [PATCH] don't pass AT_SYMLINK_NOFOLLOW flag to faccessat() |
| |
| Avoid using AT_SYMLINK_NOFOLLOW flag. It doesn't seem like the right |
| thing to do and it's not portable (not supported by musl). See: |
| |
| http://lists.landley.net/pipermail/toybox-landley.net/2014-September/003610.html |
| http://www.openwall.com/lists/musl/2015/02/05/2 |
| |
| Note that laccess() is never passing AT_EACCESS so a lot of the |
| discussion in the links above doesn't apply. Note also that |
| (currently) all systemd callers of laccess() pass mode as F_OK, so |
| only check for existence of a file, not access permissions. |
| Therefore, in this case, the only distiction between faccessat() |
| with (flag == 0) and (flag == AT_SYMLINK_NOFOLLOW) is the behaviour |
| for broken symlinks; laccess() on a broken symlink will succeed with |
| (flag == AT_SYMLINK_NOFOLLOW) and fail (flag == 0). |
| |
| The laccess() macros was added to systemd some time ago and it's not |
| clear if or why it needs to return success for broken symlinks. Maybe |
| just historical and not actually necessary or desired behaviour? |
| |
| Upstream-Status: Inappropriate [musl specific] |
| |
| Signed-off-by: Andre McCurdy <armccurdy@gmail.com> |
| |
| --- |
| src/basic/fs-util.h | 23 +++++++++++++++++++++-- |
| src/shared/base-filesystem.c | 6 +++--- |
| 2 files changed, 24 insertions(+), 5 deletions(-) |
| |
| --- a/src/basic/fs-util.h |
| +++ b/src/basic/fs-util.h |
| @@ -46,8 +46,27 @@ int futimens_opath(int fd, const struct |
| int fd_warn_permissions(const char *path, int fd); |
| int stat_warn_permissions(const char *path, const struct stat *st); |
| |
| +/* |
| + Avoid using AT_SYMLINK_NOFOLLOW flag. It doesn't seem like the right thing to |
| + do and it's not portable (not supported by musl). See: |
| + |
| + http://lists.landley.net/pipermail/toybox-landley.net/2014-September/003610.html |
| + http://www.openwall.com/lists/musl/2015/02/05/2 |
| + |
| + Note that laccess() is never passing AT_EACCESS so a lot of the discussion in |
| + the links above doesn't apply. Note also that (currently) all systemd callers |
| + of laccess() pass mode as F_OK, so only check for existence of a file, not |
| + access permissions. Therefore, in this case, the only distiction between |
| + faccessat() with (flag == 0) and (flag == AT_SYMLINK_NOFOLLOW) is the |
| + behaviour for broken symlinks; laccess() on a broken symlink will succeed |
| + with (flag == AT_SYMLINK_NOFOLLOW) and fail (flag == 0). |
| + |
| + The laccess() macros was added to systemd some time ago and it's not clear if |
| + or why it needs to return success for broken symlinks. Maybe just historical |
| + and not actually necessary or desired behaviour? |
| +*/ |
| #define laccess(path, mode) \ |
| - RET_NERRNO(faccessat(AT_FDCWD, (path), (mode), AT_SYMLINK_NOFOLLOW)) |
| + RET_NERRNO(faccessat(AT_FDCWD, (path), (mode), 0)) |
| |
| int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode); |
| int touch(const char *path); |
| --- a/src/shared/base-filesystem.c |
| +++ b/src/shared/base-filesystem.c |
| @@ -117,7 +117,7 @@ int base_filesystem_create(const char *r |
| return log_error_errno(errno, "Failed to open root file system: %m"); |
| |
| for (size_t i = 0; i < ELEMENTSOF(table); i++) { |
| - if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0) |
| + if (faccessat(fd, table[i].dir, F_OK, 0) >= 0) |
| continue; |
| |
| if (table[i].target) { |
| @@ -125,7 +125,7 @@ int base_filesystem_create(const char *r |
| |
| /* check if one of the targets exists */ |
| NULSTR_FOREACH(s, table[i].target) { |
| - if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0) |
| + if (faccessat(fd, s, F_OK, 0) < 0) |
| continue; |
| |
| /* check if a specific file exists at the target path */ |
| @@ -136,7 +136,7 @@ int base_filesystem_create(const char *r |
| if (!p) |
| return log_oom(); |
| |
| - if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0) |
| + if (faccessat(fd, p, F_OK, 0) < 0) |
| continue; |
| } |
| |