landlock: Fix warning from KUnit tests

get_id_range() expects a positive value as first argument but
get_random_u8() can return 0.  Fix this by clamping it.

Validated by running the test in a for loop for 1000 times.

Note that MAX() is wrong as it is only supposed to be used for
constants, but max() is good here.

  [..]     ok 9 test_range2_rand1
  [..]     ok 10 test_range2_rand2
  [..]     ok 11 test_range2_rand15
  [..] ------------[ cut here ]------------
  [..] WARNING: CPU: 6 PID: 104 at security/landlock/id.c:99 test_range2_rand16 (security/landlock/id.c:99 (discriminator 1) security/landlock/id.c:234 (discriminator 1))
  [..] Modules linked in:
  [..] CPU: 6 UID: 0 PID: 104 Comm: kunit_try_catch Tainted: G                 N  6.16.0-rc1-dev-00001-g314a2f98b65f #1 PREEMPT(undef)
  [..] Tainted: [N]=TEST
  [..] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
  [..] RIP: 0010:test_range2_rand16 (security/landlock/id.c:99 (discriminator 1) security/landlock/id.c:234 (discriminator 1))
  [..] Code: 49 c7 c0 10 70 30 82 4c 89 ff 48 c7 c6 a0 63 1e 83 49 c7 45 a0 e0 63 1e 83 e8 3f 95 17 00 e9 1f ff ff ff 0f 0b e9 df fd ff ff <0f> 0b ba 01 00 00 00 e9 68 fe ff ff 49 89 45 a8 49 8d 4d a0 45 31

  [..] RSP: 0000:ffff888104eb7c78 EFLAGS: 00010246
  [..] RAX: 0000000000000000 RBX: 000000000870822c RCX: 0000000000000000
            ^^^^^^^^^^^^^^^^
  [..]
  [..] Call Trace:
  [..]
  [..] ---[ end trace 0000000000000000 ]---
  [..]     ok 12 test_range2_rand16
  [..] # landlock_id: pass:12 fail:0 skip:0 total:12
  [..] # Totals: pass:12 fail:0 skip:0 total:12
  [..] ok 1 landlock_id

Fixes: d9d2a68ed44b ("landlock: Add unique ID generator")
Signed-off-by: Tingmao Wang <m@maowtm.org>
Link: https://lore.kernel.org/r/73e28efc5b8cc394608b99d5bc2596ca917d7c4a.1750003733.git.m@maowtm.org
[mic: Minor cosmetic improvements]
Signed-off-by: Mickaël Salaün <mic@digikod.net>

diff --git a/security/landlock/id.c b/security/landlock/id.c
index 56f7cc0fc7440fb2fbe122c6f1b28d2733d1c606..838c3ed7bb822ee7fe230d2fbfb7c7f572c8b427 100644 (file)
--- a/security/landlock/id.c
+++ b/security/landlock/id.c
@@ -119,6 +119,12 @@ static u64 get_id_range(size_t number_of_ids, atomic64_t *const counter,
 
 #ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST
 
+static u8 get_random_u8_positive(void)
+{
+       /* max() evaluates its arguments once. */
+       return max(1, get_random_u8());
+}
+
 static void test_range1_rand0(struct kunit *const test)
 {
        atomic64_t counter;
@@ -127,9 +133,10 @@ static void test_range1_rand0(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(1, &counter, 0), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 1);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 1);
 }
 
 static void test_range1_rand1(struct kunit *const test)
@@ -140,9 +147,10 @@ static void test_range1_rand1(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(1, &counter, 1), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 2);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 2);
 }
 
 static void test_range1_rand15(struct kunit *const test)
@@ -153,9 +161,10 @@ static void test_range1_rand15(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(1, &counter, 15), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 16);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 16);
 }
 
 static void test_range1_rand16(struct kunit *const test)
@@ -166,9 +175,10 @@ static void test_range1_rand16(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(1, &counter, 16), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 1);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 1);
 }
 
 static void test_range2_rand0(struct kunit *const test)
@@ -179,9 +189,10 @@ static void test_range2_rand0(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(2, &counter, 0), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 2);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 2);
 }
 
 static void test_range2_rand1(struct kunit *const test)
@@ -192,9 +203,10 @@ static void test_range2_rand1(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(2, &counter, 1), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 3);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 3);
 }
 
 static void test_range2_rand2(struct kunit *const test)
@@ -205,9 +217,10 @@ static void test_range2_rand2(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(2, &counter, 2), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 4);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 4);
 }
 
 static void test_range2_rand15(struct kunit *const test)
@@ -218,9 +231,10 @@ static void test_range2_rand15(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(2, &counter, 15), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 17);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 17);
 }
 
 static void test_range2_rand16(struct kunit *const test)
@@ -231,9 +245,10 @@ static void test_range2_rand16(struct kunit *const test)
        init = get_random_u32();
        atomic64_set(&counter, init);
        KUNIT_EXPECT_EQ(test, get_id_range(2, &counter, 16), init);
-       KUNIT_EXPECT_EQ(
-               test, get_id_range(get_random_u8(), &counter, get_random_u8()),
-               init + 2);
+       KUNIT_EXPECT_EQ(test,
+                       get_id_range(get_random_u8_positive(), &counter,
+                                    get_random_u8()),
+                       init + 2);
 }
 
 #endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */