Fix prctl return code/errno handling in libcap.

Bug reported by Anderson Toshiyuki Sasaki:

   https://bugzilla.kernel.org/show_bug.cgi?id=215772

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>

2 files changed, 37 insertions, 26 deletions

diff --git a/libcap/cap_proc.c b/libcap/cap_proc.c
index 65204bf..0ce5db7 100644
--- a/libcap/cap_proc.c
+++ b/libcap/cap_proc.c
@@ -135,7 +135,13 @@ static int _libcap_wprctl3(struct syscaller_s *sc,
 			   long int pr_cmd, long int arg1, long int arg2)
 {
     if (_libcap_overrode_syscalls) {
-	return sc->three(SYS_prctl, pr_cmd, arg1, arg2);
+	int result;
+	result = sc->three(SYS_prctl, pr_cmd, arg1, arg2);
+	if (result >= 0) {
+	    return result;
+	}
+	errno = -result;
+	return -1;
     }
     return prctl(pr_cmd, arg1, arg2, 0, 0, 0);
 }
@@ -145,7 +151,13 @@ static int _libcap_wprctl6(struct syscaller_s *sc,
 			   long int arg3, long int arg4, long int arg5)
 {
     if (_libcap_overrode_syscalls) {
-	return sc->six(SYS_prctl, pr_cmd, arg1, arg2, arg3, arg4, arg5);
+	int result;
+	result = sc->six(SYS_prctl, pr_cmd, arg1, arg2, arg3, arg4, arg5);
+	if (result >= 0) {
+	    return result;
+	}
+	errno = -result;
+	return -1;
     }
     return prctl(pr_cmd, arg1, arg2, arg3, arg4, arg5);
 }
@@ -271,26 +283,12 @@ int capsetp(pid_t pid, cap_t cap_d)
 
 int cap_get_bound(cap_value_t cap)
 {
-    int result;
-
-    result = prctl(PR_CAPBSET_READ, pr_arg(cap), pr_arg(0));
-    if (result < 0) {
-	errno = -result;
-	return -1;
-    }
-    return result;
+    return prctl(PR_CAPBSET_READ, pr_arg(cap), pr_arg(0));
 }
 
 static int _cap_drop_bound(struct syscaller_s *sc, cap_value_t cap)
 {
-    int result;
-
-    result = _libcap_wprctl3(sc, PR_CAPBSET_DROP, pr_arg(cap), pr_arg(0));
-    if (result < 0) {
-	errno = -result;
-	return -1;
-    }
-    return result;
+    return _libcap_wprctl3(sc, PR_CAPBSET_DROP, pr_arg(cap), pr_arg(0));
 }
 
 /* drop a capability from the bounding set */
@@ -316,7 +314,7 @@ int cap_get_ambient(cap_value_t cap)
 static int _cap_set_ambient(struct syscaller_s *sc,
 			    cap_value_t cap, cap_flag_value_t set)
 {
-    int result, val;
+    int val;
     switch (set) {
     case CAP_SET:
 	val = PR_CAP_AMBIENT_RAISE;
@@ -328,13 +326,8 @@ static int _cap_set_ambient(struct syscaller_s *sc,
 	errno = EINVAL;
 	return -1;
     }
-    result = _libcap_wprctl6(sc, PR_CAP_AMBIENT, pr_arg(val), pr_arg(cap),
-			     pr_arg(0), pr_arg(0), pr_arg(0));
-    if (result < 0) {
-	errno = -result;
-	return -1;
-    }
-    return result;
+    return _libcap_wprctl6(sc, PR_CAP_AMBIENT, pr_arg(val), pr_arg(cap),
+			   pr_arg(0), pr_arg(0), pr_arg(0));
 }
 
 /*
diff --git a/libcap/cap_test.c b/libcap/cap_test.c
index 39df261..68b6a13 100644
--- a/libcap/cap_test.c
+++ b/libcap/cap_test.c
@@ -254,6 +254,21 @@ drop_c:
     return retval;
 }
 
+static int test_prctl(void)
+{
+    int ret, retval=0;
+    errno = 0;
+    ret = cap_get_bound((cap_value_t) -1);
+    if (ret != -1) {
+	printf("cap_get_bound(-1) did not return error: %d\n", ret);
+	retval = -1;
+    } else if (errno != EINVAL) {
+	perror("cap_get_bound(-1) errno != EINVAL");
+	retval = -1;
+    }
+    return retval;
+}
+
 int main(int argc, char **argv) {
     int result = 0;
 
@@ -269,6 +284,9 @@ int main(int argc, char **argv) {
     printf("test_alloc: being called\n");
     fflush(stdout);
     result = test_alloc() | result;
+    printf("test_prctl: being called\n");
+    fflush(stdout);
+    result = test_prctl() | result;
     printf("tested\n");
     fflush(stdout);