In this PR we are dealing with a missing .UBSAN_BOUNDS, so the out-of-bounds access in the test makes the program crash before a UBSan diagnostic was emitted. In C and C++, c_genericize gets
a[b] = a[b] | c; but in C, both a[b] are one identical shared tree (not in C++ because cp_fold/ARRAY_REF created two same but not identical trees). Since ubsan_walk_array_refs_r keeps a pset, in C we produce a[.UBSAN_BOUNDS (0B, SAVE_EXPR <b>, 8);, SAVE_EXPR <b>;] = a[b] | c; because the LHS is walked before the RHS. Since r7-1900, we gimplify the RHS before the LHS. So the statement above gets gimplified into _1 = a[b]; c.0_2 = c; b.1 = b; .UBSAN_BOUNDS (0B, b.1, 8); With this patch we produce: a[b] = a[.UBSAN_BOUNDS (0B, SAVE_EXPR <b>, 8);, SAVE_EXPR <b>;] | c; which gets gimplified into: b.0 = b; .UBSAN_BOUNDS (0B, b.0, 8); _1 = a[b.0]; therefore we emit a runtime error before making the bad array access. I think it's OK that only the RHS gets a .UBSAN_BOUNDS, as in few lines above: the instrumented array access dominates the array access on the LHS, and I've verified that b = 0; a[b] = (a[b], b = -32768, a[0] | c); works as expected: the inner a[b] is OK but we do emit an error for the a[b] on the LHS. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/12? PR sanitizer/108060 PR sanitizer/109050 gcc/c-family/ChangeLog: * c-gimplify.cc (ubsan_walk_array_refs_r): For a MODIFY_EXPR, instrument the RHS before the LHS. gcc/testsuite/ChangeLog: * c-c++-common/ubsan/bounds-17.c: New test. * c-c++-common/ubsan/bounds-18.c: New test. * c-c++-common/ubsan/bounds-19.c: New test. * c-c++-common/ubsan/bounds-20.c: New test. --- gcc/c-family/c-gimplify.cc | 12 ++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-17.c | 17 +++++++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-18.c | 17 +++++++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-19.c | 20 ++++++++++++++++++++ gcc/testsuite/c-c++-common/ubsan/bounds-20.c | 16 ++++++++++++++++ 5 files changed, 82 insertions(+) create mode 100644 gcc/testsuite/c-c++-common/ubsan/bounds-17.c create mode 100644 gcc/testsuite/c-c++-common/ubsan/bounds-18.c create mode 100644 gcc/testsuite/c-c++-common/ubsan/bounds-19.c create mode 100644 gcc/testsuite/c-c++-common/ubsan/bounds-20.c diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc index 74b276b2b26..ef5c7d919fc 100644 --- a/gcc/c-family/c-gimplify.cc +++ b/gcc/c-family/c-gimplify.cc @@ -106,6 +106,18 @@ ubsan_walk_array_refs_r (tree *tp, int *walk_subtrees, void *data) } else if (TREE_CODE (*tp) == ARRAY_REF) ubsan_maybe_instrument_array_ref (tp, false); + else if (TREE_CODE (*tp) == MODIFY_EXPR) + { + /* Since r7-1900, we gimplify RHS before LHS. Consider + a[b] |= c; + wherein we can have a single shared tree a[b] in both LHS and RHS. + If we only instrument the LHS and the access is invalid, the program + could crash before emitting a UBSan error. So instrument the RHS + first. */ + *walk_subtrees = 0; + walk_tree (&TREE_OPERAND (*tp, 1), ubsan_walk_array_refs_r, pset, pset); + walk_tree (&TREE_OPERAND (*tp, 0), ubsan_walk_array_refs_r, pset, pset); + } return NULL_TREE; } diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-17.c b/gcc/testsuite/c-c++-common/ubsan/bounds-17.c new file mode 100644 index 00000000000..b727e3235b8 --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-17.c @@ -0,0 +1,17 @@ +/* PR sanitizer/108060 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds" } */ +/* { dg-skip-if "" { *-*-* } "-flto" } */ +/* { dg-shouldfail "ubsan" } */ + +int a[8]; +int c; + +int +main () +{ + int b = -32768; + a[b] |= c; +} + +/* { dg-output "index -32768 out of bounds for type 'int \\\[8\\\]'" } */ diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-18.c b/gcc/testsuite/c-c++-common/ubsan/bounds-18.c new file mode 100644 index 00000000000..556abc0e1c0 --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-18.c @@ -0,0 +1,17 @@ +/* PR sanitizer/108060 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds" } */ +/* { dg-skip-if "" { *-*-* } "-flto" } */ +/* { dg-shouldfail "ubsan" } */ + +int a[8]; +int c; + +int +main () +{ + int b = -32768; + a[b] = a[b] | c; +} + +/* { dg-output "index -32768 out of bounds for type 'int \\\[8\\\]'" } */ diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-19.c b/gcc/testsuite/c-c++-common/ubsan/bounds-19.c new file mode 100644 index 00000000000..54217ae399f --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-19.c @@ -0,0 +1,20 @@ +/* PR sanitizer/108060 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds" } */ +/* { dg-skip-if "" { *-*-* } "-flto" } */ +/* { dg-shouldfail "ubsan" } */ + +int a[8]; +int a2[18]; +int c; + +int +main () +{ + int b = 0; + a[0] = (a2[b], b = -32768, a[0] | c); + b = 0; + a[b] = (a[b], b = -32768, a[0] | c); +} + +/* { dg-output "index -32768 out of bounds for type 'int \\\[8\\\]'" } */ diff --git a/gcc/testsuite/c-c++-common/ubsan/bounds-20.c b/gcc/testsuite/c-c++-common/ubsan/bounds-20.c new file mode 100644 index 00000000000..a78c67129e0 --- /dev/null +++ b/gcc/testsuite/c-c++-common/ubsan/bounds-20.c @@ -0,0 +1,16 @@ +/* PR sanitizer/109050 */ +/* { dg-do run } */ +/* { dg-options "-fsanitize=bounds -fno-sanitize-recover=all" } */ +/* { dg-shouldfail "ubsan" } */ + +long a; +int b; +int +main () +{ + int c[4] = {0, 1, 2, 3}; + a = 0; + c[a - 9806816] |= b; +} + +/* { dg-output "index -9806816 out of bounds for type 'int \\\[4\\\]'" } */ base-commit: 2e3dd14dd287ca94b72c36ed28a1ae30887f77ce -- 2.39.2