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selftest/vm: verify remap destination address in mremap_test
[ Upstream commit 18d609daa5
]
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>
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1 changed files with 24 additions and 0 deletions
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@ -66,6 +66,30 @@ enum {
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.expect_failure = should_fail \
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}
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/*
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* Returns false if the requested remap region overlaps with an
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* existing mapping (e.g text, stack) else returns true.
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*/
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static bool is_remap_region_valid(void *addr, unsigned long long size)
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{
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void *remap_addr = NULL;
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bool ret = true;
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/* Use MAP_FIXED_NOREPLACE flag to ensure region is not mapped */
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remap_addr = mmap(addr, size, PROT_READ | PROT_WRITE,
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MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
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-1, 0);
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if (remap_addr == MAP_FAILED) {
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if (errno == EEXIST)
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ret = false;
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} else {
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munmap(remap_addr, size);
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}
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return ret;
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}
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/* Returns mmap_min_addr sysctl tunable from procfs */
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static unsigned long long get_mmap_min_addr(void)
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{
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