From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27A7A3D6D for ; Thu, 21 Apr 2022 23:35:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E24B5C385A7; Thu, 21 Apr 2022 23:35:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1650584153; bh=rlWd4GU0TXuFAdVrmoDjHHyTBnnvfudPC1YHq9S16ME=; h=Date:To:From:In-Reply-To:Subject:From; b=TOFwfCFTmU6WrBcbhovLgtQNZWBTFVEbu/WxV+i+u1wBHVhWtsBY85Yke79pr+qgx QAtxDXnV7KwUsbC1rhc8ib4YbQBBDsKSHVU3XcaZSMDJOEKi2UPWiR9yJ3f+YgGtFe Ih7xjUpD8dHvq/NGn43Uk7O/LE4SEa8GeSOQ6Mxk= Date: Thu, 21 Apr 2022 16:35:52 -0700 To: skhan@linuxfoundation.org,sidhartha.kumar@oracle.com,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220421163508.66028a9ac2d9fb6ea05b1342@linux-foundation.org> Subject: [patch 07/13] selftest/vm: verify remap destination address in mremap_test Message-Id: <20220421233552.E24B5C385A7@smtp.kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: From: Sidhartha Kumar Subject: selftest/vm: verify remap destination address in mremap_test 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 Reviewed-by: Shuah Khan Signed-off-by: Andrew Morton --- tools/testing/selftests/vm/mremap_test.c | 42 +++++++++++++++++++-- 1 file changed, 39 insertions(+), 3 deletions(-) --- 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 #include #include +#include #include "../kselftest.h" @@ -64,6 +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) { @@ -111,8 +136,8 @@ retry: 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; @@ -179,9 +204,20 @@ 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 (!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) { _