From 5d4c6b2f4b88b69b31f967371d2a6136c65dc3fd Mon Sep 17 00:00:00 2001
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From: Andre McCurdy <armccurdy@gmail.com>
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Date: Tue, 10 Oct 2017 14:33:30 -0700
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Subject: [PATCH] don't pass AT_SYMLINK_NOFOLLOW flag to faccessat()
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Avoid using AT_SYMLINK_NOFOLLOW flag. It doesn't seem like the right
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thing to do and it's not portable (not supported by musl). See:
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http://lists.landley.net/pipermail/toybox-landley.net/2014-September/003610.html
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http://www.openwall.com/lists/musl/2015/02/05/2
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Note that laccess() is never passing AT_EACCESS so a lot of the
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discussion in the links above doesn't apply. Note also that
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(currently) all systemd callers of laccess() pass mode as F_OK, so
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only check for existence of a file, not access permissions.
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Therefore, in this case, the only distiction between faccessat()
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with (flag == 0) and (flag == AT_SYMLINK_NOFOLLOW) is the behaviour
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for broken symlinks; laccess() on a broken symlink will succeed with
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(flag == AT_SYMLINK_NOFOLLOW) and fail (flag == 0).
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The laccess() macros was added to systemd some time ago and it's not
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clear if or why it needs to return success for broken symlinks. Maybe
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just historical and not actually necessary or desired behaviour?
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Upstream-Status: Inappropriate [musl specific]
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Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
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---
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src/basic/fs-util.h | 23 +++++++++++++++++++++--
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src/shared/base-filesystem.c | 6 +++---
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2 files changed, 24 insertions(+), 5 deletions(-)
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diff --git a/src/basic/fs-util.h b/src/basic/fs-util.h
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index 7f15b558ca..4263298cad 100644
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--- a/src/basic/fs-util.h
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+++ b/src/basic/fs-util.h
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@@ -47,8 +47,27 @@ int futimens_opath(int fd, const struct timespec ts[2]);
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int fd_warn_permissions(const char *path, int fd);
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int stat_warn_permissions(const char *path, const struct stat *st);
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-#define laccess(path, mode) \
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- (faccessat(AT_FDCWD, (path), (mode), AT_SYMLINK_NOFOLLOW) < 0 ? -errno : 0)
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+/*
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+ Avoid using AT_SYMLINK_NOFOLLOW flag. It doesn't seem like the right thing to
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+ do and it's not portable (not supported by musl). See:
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+
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+ http://lists.landley.net/pipermail/toybox-landley.net/2014-September/003610.html
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+ http://www.openwall.com/lists/musl/2015/02/05/2
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+
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+ Note that laccess() is never passing AT_EACCESS so a lot of the discussion in
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+ the links above doesn't apply. Note also that (currently) all systemd callers
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+ of laccess() pass mode as F_OK, so only check for existence of a file, not
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+ access permissions. Therefore, in this case, the only distiction between
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+ faccessat() with (flag == 0) and (flag == AT_SYMLINK_NOFOLLOW) is the
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+ behaviour for broken symlinks; laccess() on a broken symlink will succeed
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+ with (flag == AT_SYMLINK_NOFOLLOW) and fail (flag == 0).
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+
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+ The laccess() macros was added to systemd some time ago and it's not clear if
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+ or why it needs to return success for broken symlinks. Maybe just historical
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+ and not actually necessary or desired behaviour?
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+*/
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+
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+#define laccess(path, mode) faccessat(AT_FDCWD, (path), (mode), 0)
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int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode);
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int touch(const char *path);
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diff --git a/src/shared/base-filesystem.c b/src/shared/base-filesystem.c
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index 016eb7b82a..b1967f9f2f 100644
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--- a/src/shared/base-filesystem.c
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+++ b/src/shared/base-filesystem.c
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@@ -53,7 +53,7 @@ int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
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return log_error_errno(errno, "Failed to open root file system: %m");
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for (size_t i = 0; i < ELEMENTSOF(table); i++) {
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- if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
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+ if (faccessat(fd, table[i].dir, F_OK, 0) >= 0)
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continue;
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if (table[i].target) {
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@@ -61,7 +61,7 @@ int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
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/* check if one of the targets exists */
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NULSTR_FOREACH(s, table[i].target) {
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- if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
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+ if (faccessat(fd, s, F_OK, 0) < 0)
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continue;
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/* check if a specific file exists at the target path */
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@@ -72,7 +72,7 @@ int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
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if (!p)
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return log_oom();
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- if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
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+ if (faccessat(fd, p, F_OK, 0) < 0)
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continue;
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}
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