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selftest/vm: verify remap destination address in mremap_test 

[ 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>
This commit is contained in:
Sidhartha Kumar 2022-04-21 16:35:52 -07:00 committed by Greg Kroah-Hartman
parent a17404fcbf
commit 2688d967ec
1 changed files with 39 additions and 3 deletions
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42
tools/testing/selftests/vm/mremap_test.c
View File

@ -10,6 +10,7 @@
#include <string.h>
#include <sys/mman.h>
#include <time.h>
#include <stdbool.h>
#include "../kselftest.h"
@ -65,6 +66,30 @@ 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)
{
@ -112,8 +137,8 @@ static void *get_source_mapping(struct config c)
goto retry;
src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
-1, 0);
MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
-1, 0);
if (src_addr == MAP_FAILED) {
if (errno == EPERM || errno == EEXIST)
goto retry;
@ -180,9 +205,20 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
if (!((unsigned long long) addr & c.dest_alignment))
addr = (void *) ((unsigned long long) addr | c.dest_alignment);
/* Don't destroy existing mappings unless expected to overlap */
while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
/* Check for unsigned overflow */
if (addr + c.dest_alignment < addr) {
ksft_print_msg("Couldn't find a valid region to remap to\n");
ret = -1;
goto out;
}
addr += c.dest_alignment;
}
clock_gettime(CLOCK_MONOTONIC, &t_start);
dest_addr = mremap(src_addr, c.region_size, c.region_size,
MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
clock_gettime(CLOCK_MONOTONIC, &t_end);
if (dest_addr == MAP_FAILED) {