lkml.org 
[lkml]   [2022]   [May]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.17 120/140] selftest/vm: verify remap destination address in mremap_test
Date
From: Sidhartha Kumar <sidhartha.kumar@oracle.com>

[ Upstream commit 18d609daa546c919fd36b62a7b510c18de4b4af8 ]

Because mremap does not have a MAP_FIXED_NOREPLACE flag, it can destroy
existing mappings. This causes a segfault when regions such as text are
remapped and the permissions are changed.

Verify the requested mremap destination address does not overlap any
existing mappings by using mmap's MAP_FIXED_NOREPLACE flag. Keep
incrementing the destination address until a valid mapping is found or
fail the current test once the max address is reached.

Link: https://lkml.kernel.org/r/20220420215721.4868-2-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/vm/mremap_test.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/tools/testing/selftests/vm/mremap_test.c b/tools/testing/selftests/vm/mremap_test.c
index 380a4593dbd6..5ef41640d657 100644
--- a/tools/testing/selftests/vm/mremap_test.c
+++ b/tools/testing/selftests/vm/mremap_test.c
@@ -65,6 +65,30 @@ enum {
.expect_failure = should_fail \
}

+/*
+ * Returns false if the requested remap region overlaps with an
+ * existing mapping (e.g text, stack) else returns true.
+ */
+static bool is_remap_region_valid(void *addr, unsigned long long size)
+{
+ void *remap_addr = NULL;
+ bool ret = true;
+
+ /* Use MAP_FIXED_NOREPLACE flag to ensure region is not mapped */
+ remap_addr = mmap(addr, size, PROT_READ | PROT_WRITE,
+ MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
+ -1, 0);
+
+ if (remap_addr == MAP_FAILED) {
+ if (errno == EEXIST)
+ ret = false;
+ } else {
+ munmap(remap_addr, size);
+ }
+
+ return ret;
+}
+
/* Returns mmap_min_addr sysctl tunable from procfs */
static unsigned long long get_mmap_min_addr(void)
{
--
2.35.1


\
 
 \ /
  Last update: 2022-05-10 16:34    [W:1.466 / U:0.540 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site