X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=src%2Fshared%2Fcapability.c;h=915ceb9d9b1a4749206bebb638a971f7dcac156c;hb=2404701e679904979751816930101511d8ec5d49;hp=dcf7ce1a69ec58b252c4dcf1bc06ace259b5c48e;hpb=51ddf61540976fc7b09ce5ace707b27f3acc3871;p=elogind.git

diff --git a/src/shared/capability.c b/src/shared/capability.c
index dcf7ce1a6..915ceb9d9 100644
--- 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;
 
+                /* use enough bits */
+                assert(i == 64 || (keep_capabilities >> i) == 0);
+                /* don't use too many bits */
+                assert(keep_capabilities & (1ULL << (i - 1)));
+
                 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");