The patch titled Subject: selftest/vm: verify remap destination address in mremap_test has been added to the -mm tree. Its filename is selftest-vm-verify-remap-destination-address-in-mremap_test.patch
This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/selftest-vm-verify-remap-destinati... and later at https://ozlabs.org/~akpm/mmotm/broken-out/selftest-vm-verify-remap-destinati...
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------------------------------------------------------ From: Sidhartha Kumar sidhartha.kumar@oracle.com Subject: selftest/vm: verify remap destination address in mremap_test
Because mremap does not have a NOREPLACE flag, it can destroy existing mappings. This can cause a segfault if regions such as text are destroyed. Verify the requested mremap destination address does not overlap any existing mappings by using mmap's FIXED_NOREPLACE flag and checking for the EEXIST error code. Keep incrementing the destination address until a valid mapping is found or max address is reached.
Link: https://lkml.kernel.org/r/20220414171529.62058-3-sidhartha.kumar@oracle.com Signed-off-by: Sidhartha Kumar sidhartha.kumar@oracle.com Cc: Shuah Khan shuah@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
--- a/tools/testing/selftests/vm/mremap_test.c~selftest-vm-verify-remap-destination-address-in-mremap_test +++ a/tools/testing/selftests/vm/mremap_test.c @@ -10,6 +10,7 @@ #include <string.h> #include <sys/mman.h> #include <time.h> +#include <limits.h>
#include "../kselftest.h"
@@ -64,6 +65,34 @@ enum { .expect_failure = should_fail \ }
+/* + * Returns 0 if the requested remap region overlaps with an + * existing mapping (e.g text, stack) else returns 1. + */ +static int remap_region_valid(void *addr, unsigned long long size) +{ + void *remap_addr = NULL; + int ret = 1; + + if ((unsigned long long) addr > ULLONG_MAX - size) { + ksft_print_msg("Can't find a valid region to remap to\n"); + exit(KSFT_SKIP); + } + + /* 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 = 0; + } else { + munmap(remap_addr, size); + } + + return ret; +} + /* Returns mmap_min_addr sysctl */ static unsigned long long get_mmap_min_addr(void) { @@ -179,6 +208,13 @@ static long long remap_region(struct con 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 (!remap_region_valid(addr, c.region_size)) { + if (c.overlapping) + break; + addr += c.src_alignment; + } + clock_gettime(CLOCK_MONOTONIC, &t_start); dest_addr = mremap(src_addr, c.region_size, c.region_size, MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr); _
Patches currently in -mm which might be from sidhartha.kumar@oracle.com are
selftest-vm-verify-mmap-addr-in-mremap_test.patch selftest-vm-verify-remap-destination-address-in-mremap_test.patch selftest-vm-support-xfail-in-mremap_test.patch selftest-vm-add-skip-support-to-mremap_test.patch selftest-vm-clarify-error-statement-in-gup_test.patch