From 3aebd2adc30e164065327c7d3820ad98fe59cad8 Mon Sep 17 00:00:00 2001 From: Yuri Gribov Date: Sun, 14 Aug 2022 08:42:44 +0300 Subject: [PATCH] asan: fix unsafe optimization of Asan checks. gcc/ PR sanitizer/106558 * sanopt.c: Do not optimize out checks for non-SSA addresses. gcc/testsuite/ PR sanitizer/106558 * c-c++-common/asan/pr106558.c: New test. --- gcc/sanopt.cc | 40 +++++++++++++++++----- gcc/testsuite/c-c++-common/asan/pr106558.c | 23 +++++++++++++ 2 files changed, 54 insertions(+), 9 deletions(-) create mode 100644 gcc/testsuite/c-c++-common/asan/pr106558.c diff --git a/gcc/sanopt.cc b/gcc/sanopt.cc index e9d188d7889..13942a0b1da 100644 --- a/gcc/sanopt.cc +++ b/gcc/sanopt.cc @@ -80,16 +80,16 @@ struct sanopt_info /* If T has a single definition of form T = T2, return T2. */ -static tree +static gimple * maybe_get_single_definition (tree t) { if (TREE_CODE (t) == SSA_NAME) { gimple *g = SSA_NAME_DEF_STMT (t); if (gimple_assign_single_p (g)) - return gimple_assign_rhs1 (g); + return g; } - return NULL_TREE; + return NULL; } /* Tree triplet for vptr_check_map. */ @@ -618,11 +618,30 @@ maybe_optimize_ubsan_vptr_ifn (class sanopt_ctx *ctx, gimple *stmt) return true; } +/* Checks whether value of T in CHECK and USE is the same. */ + +static bool same_value_p (gimple *check, gimple *use, tree t) +{ + tree check_vuse = gimple_vuse (check); + tree use_vuse = gimple_vuse (use); + + if (TREE_CODE (t) == SSA_NAME + || is_gimple_min_invariant (t) + || ! use_vuse) + return true; + + if (check_vuse == use_vuse) + return true; + + return false; +} + /* Returns TRUE if ASan check of length LEN in block BB can be removed if preceded by checks in V. */ static bool -can_remove_asan_check (auto_vec &v, tree len, basic_block bb) +can_remove_asan_check (auto_vec &v, tree len, basic_block bb, + gimple *base_stmt, tree base_addr) { unsigned int i; gimple *g; @@ -674,8 +693,10 @@ can_remove_asan_check (auto_vec &v, tree len, basic_block bb) last_bb = imm; } - if (last_bb == gbb) - remove = true; + if (last_bb != gbb) + break; + // In case of base_addr residing in memory we also need to check aliasing + remove = ! base_addr || same_value_p (g, base_stmt, base_addr); break; } @@ -718,7 +739,8 @@ maybe_optimize_asan_check_ifn (class sanopt_ctx *ctx, gimple *stmt) auto_vec *ptr_checks = &ctx->asan_check_map.get_or_insert (ptr); - tree base_addr = maybe_get_single_definition (ptr); + gimple *base_stmt = maybe_get_single_definition (ptr); + tree base_addr = base_stmt ? gimple_assign_rhs1 (base_stmt) : NULL_TREE; auto_vec *base_checks = NULL; if (base_addr) { @@ -747,11 +769,11 @@ maybe_optimize_asan_check_ifn (class sanopt_ctx *ctx, gimple *stmt) bool remove = false; if (ptr_checks) - remove = can_remove_asan_check (*ptr_checks, len, bb); + remove = can_remove_asan_check (*ptr_checks, len, bb, NULL, NULL); if (!remove && base_checks) /* Try with base address as well. */ - remove = can_remove_asan_check (*base_checks, len, bb); + remove = can_remove_asan_check (*base_checks, len, bb, base_stmt, base_addr); if (!remove) { diff --git a/gcc/testsuite/c-c++-common/asan/pr106558.c b/gcc/testsuite/c-c++-common/asan/pr106558.c new file mode 100644 index 00000000000..d82b2dc7a83 --- /dev/null +++ b/gcc/testsuite/c-c++-common/asan/pr106558.c @@ -0,0 +1,23 @@ +/* { dg-do run } */ +/* { dg-options "-w -fpermissive" } */ +/* { dg-shouldfail "asan" } */ + +int a; +int *b = &a; +int **c = &b; +int d[1]; +int *e = &d[1]; + +static int f(int *g) { + *b = e; + *c = e; + *b = 2; + *g = 2; +} + +int main() { + f(b); + return *b; +} + +/* { dg-output "AddressSanitizer: global-buffer-overflow on address" } */ -- 2.17.1