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selftest/vm: verify mmap addr in mremap_test

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Avoid calling mmap with requested addresses that are less than the
system's mmap_min_addr.  When run as root, mmap returns EACCES when
trying to map addresses < mmap_min_addr.  This is not one of the error
codes for the condition to retry the mmap in the test.

Rather than arbitrarily retrying on EACCES, don't attempt an mmap until
addr > vm.mmap_min_addr.

Add a munmap call after an alignment check as the mappings are retained
after the retry and can reach the vm.max_map_count sysctl.

Link: https://lkml.kernel.org/r/20220420215721.4868-1-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>
This commit is contained in:
Sidhartha Kumar 2022-04-21 16:35:49 -07:00 committed by Linus Torvalds
parent 5f24d5a579
commit 9c85a9bae2
1 changed files with 40 additions and 1 deletions
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41
tools/testing/selftests/vm/mremap_test.c
View File

@ -6,6 +6,7 @@
#include <errno.h> #include <errno.h>
#include <stdlib.h> #include <stdlib.h>
#include <stdio.h>
#include <string.h> #include <string.h>
#include <sys/mman.h> #include <sys/mman.h>
#include <time.h> #include <time.h>
@ -63,6 +64,35 @@ enum {
.expect_failure = should_fail \ .expect_failure = should_fail \
} }
/* Returns mmap_min_addr sysctl tunable from procfs */
static unsigned long long get_mmap_min_addr(void)
{
FILE *fp;
int n_matched;
static unsigned long long addr;
if (addr)
return addr;
fp = fopen("/proc/sys/vm/mmap_min_addr", "r");
if (fp == NULL) {
ksft_print_msg("Failed to open /proc/sys/vm/mmap_min_addr: %s\n",
strerror(errno));
exit(KSFT_SKIP);
}
n_matched = fscanf(fp, "%llu", &addr);
if (n_matched != 1) {
ksft_print_msg("Failed to read /proc/sys/vm/mmap_min_addr: %s\n",
strerror(errno));
fclose(fp);
exit(KSFT_SKIP);
}
fclose(fp);
return addr;
}
/* /*
* Returns the start address of the mapping on success, else returns * Returns the start address of the mapping on success, else returns
* NULL on failure. * NULL on failure.
@ -71,8 +101,15 @@ static void *get_source_mapping(struct config c)
{ {
unsigned long long addr = 0ULL; unsigned long long addr = 0ULL;
void *src_addr = NULL; void *src_addr = NULL;
unsigned long long mmap_min_addr;
mmap_min_addr = get_mmap_min_addr();
retry: retry:
addr += c.src_alignment; addr += c.src_alignment;
if (addr < mmap_min_addr)
goto retry;
src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE, src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED, MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
-1, 0); -1, 0);
@ -90,8 +127,10 @@ retry:
* alignment in the tests. * alignment in the tests.
*/ */
if (((unsigned long long) src_addr & (c.src_alignment - 1)) || if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
!((unsigned long long) src_addr & c.src_alignment)) !((unsigned long long) src_addr & c.src_alignment)) {
munmap(src_addr, c.region_size);
goto retry; goto retry;
}
if (!src_addr) if (!src_addr)
goto error; goto error;