[LTP] [PATCH v6] hugemmap37: Migrate truncate_sigbus_versus_oom from libhugetlbfs

[“Samir <samir@linux.ibm.com>]

Some kernels have a bug in the positioning of the test against
i_size. This bug means that attempting to instantiate a page
beyond the end of a hugepage file can result in an OOM and SIGKILL
instead of the correct SIGBUS.

This test verifies that accessing memory beyond a truncated hugepage
file correctly triggers SIGBUS rather than causing an OOM condition.

Signed-off-by: Samir <samir@linux.ibm.com>
---
v6:
1. Fixed description: Removed dangling comma and improved clarity
2. Added 'static' keyword to setup() and cleanup() functions
3. Fixed signal handler initialization:
   - Zero-initialized struct sigaction with = {}
   - Added sigemptyset(&sa.sa_mask)
   - Removed SA_SIGINFO flag (using sa_handler, not sa_sigaction)
4. Removed dead code: Deleted unused totpages assignment from setup()
5. Fixed resource leaks in run_test():
   - Added SAFE_MUNMAP() for both mapped regions (p and q)
   - Added SAFE_CLOSE() for both file descriptors (fd and fdx)
   - Reset fd and fdx to -1 after closing
6. Fixed cleanup() checks: Changed 'if (fd > 0)' to 'if (fd != -1)'
7. Initialized file descriptors to -1 at declaration
---
 runtest/hugetlb                               |   1 +
 testcases/kernel/mem/.gitignore               |   1 +
 .../kernel/mem/hugetlb/hugemmap/hugemmap37.c  | 106 ++++++++++++++++++
 3 files changed, 108 insertions(+)
 create mode 100644 testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c

diff --git a/runtest/hugetlb b/runtest/hugetlb
index 0896d3c94..8aaafeee3 100644
--- a/runtest/hugetlb
+++ b/runtest/hugetlb
@@ -36,6 +36,7 @@ hugemmap30 hugemmap30
 hugemmap31 hugemmap31
 hugemmap32 hugemmap32
 hugemmap34 hugemmap34
+hugemmap37 hugemmap37
 hugemmap05_1 hugemmap05 -m
 hugemmap05_2 hugemmap05 -s
 hugemmap05_3 hugemmap05 -s -m
diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
index b4455de51..38d428fe8 100644
--- a/testcases/kernel/mem/.gitignore
+++ b/testcases/kernel/mem/.gitignore
@@ -36,6 +36,7 @@
 /hugetlb/hugemmap/hugemmap31
 /hugetlb/hugemmap/hugemmap32
 /hugetlb/hugemmap/hugemmap34
+/hugetlb/hugemmap/hugemmap37
 /hugetlb/hugeshmat/hugeshmat01
 /hugetlb/hugeshmat/hugeshmat02
 /hugetlb/hugeshmat/hugeshmat03
diff --git a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c
new file mode 100644
index 000000000..06813b976
--- /dev/null
+++ b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap37.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
+ */
+
+/*\
+ * Some kernels have a bug in the positioning of the test against
+ * i_size. This bug means that attempting to instantiate a page
+ * beyond the end of a hugepage file can result in an OOM and SIGKILL
+ * instead of the correct SIGBUS.
+ *
+ * The test:
+ * - Creates a hugepage file and maps it
+ * - Truncates the file to 0 size
+ * - Allocates all available hugepages to create memory pressure
+ * - Attempts to access the mapped memory
+ * - Verifies SIGBUS is received (correct behavior)
+ */
+
+#include "hugetlb.h"
+#include <setjmp.h>
+#include <signal.h>
+
+#define MNTPOINT "hugetlbfs/"
+static int fd = -1, fdx = -1;
+
+static unsigned long long hpage_size;
+static unsigned long totpages;
+
+static sigjmp_buf sig_escape;
+static volatile int test_pass;
+
+static void sigbus_handler(int signum LTP_ATTRIBUTE_UNUSED)
+{
+	test_pass = 1;
+	siglongjmp(sig_escape, 17);
+}
+
+static void run_test(void)
+{
+	void *p, *q;
+	unsigned long i;
+
+	test_pass = 0;
+
+	fd = tst_creat_unlinked(MNTPOINT, 0, 0600);
+	p = SAFE_MMAP(NULL, hpage_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	SAFE_FTRUNCATE(fd, 0);
+
+	fdx = tst_creat_unlinked(MNTPOINT, 0, 0600);
+	totpages = SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE);
+	q = SAFE_MMAP(NULL, totpages * hpage_size, PROT_READ | PROT_WRITE, MAP_SHARED,
+			fdx, 0);
+	/* Touch the pages to ensure they're removed from the pool */
+	for (i = 0; i < totpages; i++) {
+		volatile char *x = (volatile char *)q + i * hpage_size;
+		*x = 0;
+	}
+	/* SIGBUS is what *should* happen */
+	SAFE_FTRUNCATE(fdx, 0);
+	if (sigsetjmp(sig_escape, 1) == 0)
+		*((volatile unsigned int *)p);
+
+	if (test_pass)
+		tst_res(TPASS, "Expected SIGBUS triggered");
+	else
+		tst_res(TFAIL, "Didn't SIGBUS");
+
+	SAFE_MUNMAP(p, hpage_size);
+	SAFE_MUNMAP(q, totpages * hpage_size);
+	SAFE_CLOSE(fd);
+	SAFE_CLOSE(fdx);
+	fd = -1;
+	fdx = -1;
+}
+
+static void setup(void)
+{
+	struct sigaction sa = {};
+
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = 0;
+	sa.sa_handler = sigbus_handler;
+	SAFE_SIGACTION(SIGBUS, &sa, NULL);
+	hpage_size = tst_get_hugepage_size();
+}
+
+static void cleanup(void)
+{
+	if (fd != -1)
+		SAFE_CLOSE(fd);
+	if (fdx != -1)
+		SAFE_CLOSE(fdx);
+}
+
+static struct tst_test test = {
+	.tags = (struct tst_tag[]){{"linux-git", "ebed4bfc8da8"}, {}},
+	.needs_root = 1,
+	.mntpoint = MNTPOINT,
+	.needs_hugetlbfs = 1,
+	.needs_tmpdir = 1,
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = run_test,
+	.hugepages = {1, TST_NEEDS},
+};
-- 
2.52.0


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