shared/capability: don't be too frugal on space for caps

[elogind.git] / src / shared / capability.c

diff --git a/src/shared/capability.c b/src/shared/capability.c
index dcf7ce1a69ec58b252c4dcf1bc06ace259b5c48e..57f392a4da887228c616577f63c8b37ca8ad03b5 100644 (file)
--- a/src/shared/capability.c
+++ b/src/shared/capability.c
@@ -269,12 +269,17 @@ int drop_privileges(uid_t uid, gid_t gid, uint64_t keep_capabilities) {
                 return log_oom();
 
         if (keep_capabilities) {
-                cap_value_t bits[sizeof(keep_capabilities)*8];
+                cap_value_t bits[u64log2(keep_capabilities) + 1];
 
-                for (i = 0; i < sizeof(keep_capabilities)*8; i++)
+                for (i = 0; i < ELEMENTSOF(bits); i++)
                         if (keep_capabilities & (1ULL << i))
                                 bits[j++] = i;
 
+                /* don't keep too many bits */
+                assert((keep_capabilities & (~1ULL << i)) == 0);
+                /* don't throw away too many bits */
+                assert(((keep_capabilities >> i) & (~1ULL >> i)) == 0);
+
                 if (cap_set_flag(d, CAP_EFFECTIVE, j, bits, CAP_SET) < 0 ||
                     cap_set_flag(d, CAP_PERMITTED, j, bits, CAP_SET) < 0) {
                         log_error_errno(errno, "Failed to enable capabilities bits: %m");