104 lines
3.1 KiB
Diff
104 lines
3.1 KiB
Diff
From 0744fa4f533c765d0a704fe8aa7174a0f93eb7bc Mon Sep 17 00:00:00 2001
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From: Nicolas Iooss <nicolas.iooss@m4x.org>
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Date: Thu, 22 Apr 2021 08:46:04 +0200
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Subject: [PATCH] libsepol: use checked arithmetic builtin to perform safe
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addition
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Checking whether an overflow occurred after adding two values can be
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achieved using checked arithmetic builtin functions such as:
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bool __builtin_add_overflow(type1 x, type2 y, type3 *sum);
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This function is available at least in clang
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(at least since clang 3.8.0,
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https://releases.llvm.org/3.8.0/tools/clang/docs/LanguageExtensions.html#checked-arithmetic-builtins)
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and gcc
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(https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html,
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since gcc 5 according to https://gcc.gnu.org/gcc-5/changes.html)
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Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
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---
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libsepol/src/context_record.c | 29 ++++++-----------------------
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libsepol/src/module_to_cil.c | 6 ++----
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2 files changed, 8 insertions(+), 27 deletions(-)
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diff --git a/libsepol/src/context_record.c b/libsepol/src/context_record.c
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index 317a42133884..435f788058c4 100644
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--- a/libsepol/src/context_record.c
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+++ b/libsepol/src/context_record.c
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@@ -267,31 +267,13 @@ int sepol_context_from_string(sepol_handle_t * handle,
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return STATUS_ERR;
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}
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-
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-static inline int safe_sum(size_t *sum, const size_t augends[], const size_t cnt) {
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-
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- size_t a, i;
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-
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- *sum = 0;
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- for(i=0; i < cnt; i++) {
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- /* sum should not be smaller than the addend */
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- a = augends[i];
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- *sum += a;
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- if (*sum < a) {
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- return i;
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- }
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- }
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-
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- return 0;
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-}
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-
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int sepol_context_to_string(sepol_handle_t * handle,
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const sepol_context_t * con, char **str_ptr)
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{
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int rc;
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char *str = NULL;
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- size_t total_sz, err;
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+ size_t total_sz = 0, i;
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const size_t sizes[] = {
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strlen(con->user), /* user length */
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strlen(con->role), /* role length */
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@@ -300,10 +282,11 @@ int sepol_context_to_string(sepol_handle_t * handle,
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((con->mls) ? 3 : 2) + 1 /* mls has extra ":" also null byte */
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};
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- err = safe_sum(&total_sz, sizes, ARRAY_SIZE(sizes));
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- if (err) {
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- ERR(handle, "invalid size, overflow at position: %zu", err);
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- goto err;
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+ for (i = 0; i < ARRAY_SIZE(sizes); i++) {
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+ if (__builtin_add_overflow(total_sz, sizes[i], &total_sz)) {
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+ ERR(handle, "invalid size, overflow at position: %zu", i);
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+ goto err;
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+ }
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}
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str = (char *)malloc(total_sz);
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diff --git a/libsepol/src/module_to_cil.c b/libsepol/src/module_to_cil.c
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index 58df0d4f6d77..496693f4616e 100644
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--- a/libsepol/src/module_to_cil.c
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+++ b/libsepol/src/module_to_cil.c
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@@ -1134,16 +1134,14 @@ static int name_list_to_string(char **names, unsigned int num_names, char **stri
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char *strpos;
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for (i = 0; i < num_names; i++) {
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- len += strlen(names[i]);
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- if (len < strlen(names[i])) {
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+ if (__builtin_add_overflow(len, strlen(names[i]), &len)) {
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log_err("Overflow");
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return -1;
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}
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}
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// add spaces + null terminator
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- len += num_names;
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- if (len < (size_t)num_names) {
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+ if (__builtin_add_overflow(len, (size_t)num_names, &len)) {
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log_err("Overflow");
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return -1;
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}
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--
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2.32.0
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