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basic: allow copy_rights() to work without mounted /proc

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This will be used in sysusers later on.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2021-05-24 11:33:50 +02:00
parent 335f6ab4f1
commit 0520564dcf
4 changed files with 32 additions and 10 deletions
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4
src/basic/copy.c
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@ -1243,7 +1243,7 @@ int copy_access(int fdf, int fdt) {
return 0;
}
int copy_rights(int fdf, int fdt) {
int copy_rights_with_fallback(int fdf, int fdt, const char *patht) {
struct stat st;
assert(fdf >= 0);
@ -1254,7 +1254,7 @@ int copy_rights(int fdf, int fdt) {
if (fstat(fdf, &st) < 0)
return -errno;
return fchmod_and_chown(fdt, st.st_mode & 07777, st.st_uid, st.st_gid);
return fchmod_and_chown_with_fallback(fdt, patht, st.st_mode & 07777, st.st_uid, st.st_gid);
}
int copy_xattr(int fdf, int fdt) {

5
src/basic/copy.h
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@ -64,5 +64,8 @@ static inline int copy_bytes(int fdf, int fdt, uint64_t max_bytes, CopyFlags cop
int copy_times(int fdf, int fdt, CopyFlags flags);
int copy_access(int fdf, int fdt);
int copy_rights(int fdf, int fdt);
int copy_rights_with_fallback(int fdf, int fdt, const char *patht);
static inline int copy_rights(int fdf, int fdt) {
return copy_rights_with_fallback(fdf, fdt, NULL); /* no fallback */
}
int copy_xattr(int fdf, int fdt);

28
src/basic/fs-util.c
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@ -227,7 +227,7 @@ int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
return fchmod_and_chown(fd, mode, uid, gid);
}
int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
int fchmod_and_chown_with_fallback(int fd, const char *path, mode_t mode, uid_t uid, gid_t gid) {
bool do_chown, do_chmod;
struct stat st;
int r;
@ -238,7 +238,11 @@ int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
* unaffected if the uid/gid is changed, i.e. it undoes implicit suid/sgid dropping the kernel does
* on chown().
*
* This call is happy with O_PATH fds. */
* This call is happy with O_PATH fds.
*
* If path is given, allow a fallback path which does not use /proc/self/fd/. On any normal system
* /proc will be mounted, but in certain improperly assembled environments it might not be. This is
* less secure (potential TOCTOU), so should only be used after consideration. */
if (fstat(fd, &st) < 0)
return -errno;
@ -263,8 +267,14 @@ int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
if (((minimal ^ st.st_mode) & 07777) != 0) {
r = fchmod_opath(fd, minimal & 07777);
if (r < 0)
return r;
if (r < 0) {
if (!path || r != -ENOSYS)
return r;
/* Fallback path which doesn't use /proc/self/fd/. */
if (chmod(path, minimal & 07777) < 0)
return -errno;
}
}
}
@ -274,8 +284,14 @@ int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
if (do_chmod) {
r = fchmod_opath(fd, mode & 07777);
if (r < 0)
return r;
if (r < 0) {
if (!path || r != -ENOSYS)
return r;
/* Fallback path which doesn't use /proc/self/fd/. */
if (chmod(path, mode & 07777) < 0)
return -errno;
}
}
return do_chown || do_chmod;

5
src/basic/fs-util.h
View File

@ -34,7 +34,10 @@ int readlink_value(const char *p, char **ret);
int readlink_and_make_absolute(const char *p, char **r);
int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid);
int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid);
int fchmod_and_chown_with_fallback(int fd, const char *path, mode_t mode, uid_t uid, gid_t gid);
static inline int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
return fchmod_and_chown_with_fallback(fd, NULL, mode, uid, gid); /* no fallback */
}
int fchmod_umask(int fd, mode_t mode);
int fchmod_opath(int fd, mode_t m);