Merge pull request #28423 from dvdhrm/pr/memfd

basic/memfd: untangle historic `sealed` property

src/basic/memfd-util.c

@@ -68,19 +68,40 @@ int memfd_new(const char *name) {
         return memfd_create_wrapper(name, MFD_ALLOW_SEALING | MFD_CLOEXEC | MFD_NOEXEC_SEAL);
 }
 
+int memfd_add_seals(int fd, unsigned int seals) {
+        assert(fd >= 0);
+
+        return RET_NERRNO(fcntl(fd, F_ADD_SEALS, seals));
+}
+
+int memfd_get_seals(int fd, unsigned int *ret_seals) {
+        int r;
+
+        assert(fd >= 0);
+
+        r = RET_NERRNO(fcntl(fd, F_GET_SEALS));
+        if (r < 0)
+                return r;
+
+        if (ret_seals)
+                *ret_seals = r;
+        return 0;
+}
+
 int memfd_map(int fd, uint64_t offset, size_t size, void **p) {
+        unsigned int seals;
         void *q;
-        int sealed;
+        int r;
 
         assert(fd >= 0);
         assert(size > 0);
         assert(p);
 
-        sealed = memfd_get_sealed(fd);
-        if (sealed < 0)
-                return sealed;
+        r = memfd_get_seals(fd, &seals);
+        if (r < 0)
+                return r;
 
-        if (sealed)
+        if (seals & F_SEAL_WRITE)
                 q = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, offset);
         else
                 q = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
@@ -92,28 +113,19 @@ int memfd_map(int fd, uint64_t offset, size_t size, void **p) {
 }
 
 int memfd_set_sealed(int fd) {
-        int r;
-
-        assert(fd >= 0);
-
-        r = RET_NERRNO(fcntl(fd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_EXEC | F_SEAL_SEAL));
-        if (r == -EINVAL) /* old kernel ? */
-                r = RET_NERRNO(fcntl(fd, F_ADD_SEALS, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL));
-
-        return r;
+        return memfd_add_seals(fd, F_SEAL_SEAL | F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE);
 }
 
 int memfd_get_sealed(int fd) {
+        unsigned int seals;
         int r;
 
-        assert(fd >= 0);
-
-        r = fcntl(fd, F_GET_SEALS);
+        r = memfd_get_seals(fd, &seals);
         if (r < 0)
-                return -errno;
+                return r;
 
         /* We ignore F_SEAL_EXEC here to support older kernels. */
-        return FLAGS_SET(r, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE | F_SEAL_SEAL);
+        return FLAGS_SET(seals, F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE);
 }
 
 int memfd_get_size(int fd, uint64_t *sz) {

src/basic/memfd-util.h

@@ -12,6 +12,8 @@ int memfd_new(const char *name);
 int memfd_new_and_map(const char *name, size_t sz, void **p);
 int memfd_new_and_seal(const char *name, const void *data, size_t sz);
 
+int memfd_add_seals(int fd, unsigned int seals);
+int memfd_get_seals(int fd, unsigned int *ret_seals);
 int memfd_map(int fd, uint64_t offset, size_t size, void **p);
 
 int memfd_set_sealed(int fd);