PR middle-end/77608 - missing protection on trivially detectable runtime buffer overflow gcc/ChangeLog: PR middle-end/77608 * builtins.c (compute_objsize): Handle non-constant offsets. gcc/testsuite/ChangeLog: PR middle-end/77608 * gcc.dg/Wstringop-overflow.c: New test. Index: gcc/builtins.c =================================================================== --- gcc/builtins.c (revision 254879) +++ gcc/builtins.c (working copy) @@ -3276,11 +3276,6 @@ compute_objsize (tree dest, int ostype) if (compute_builtin_object_size (dest, ostype, &size)) return build_int_cst (sizetype, size); - /* Unless computing the largest size (for memcpy and other raw memory - functions), try to determine the size of the object from its type. */ - if (!ostype) - return NULL_TREE; - if (TREE_CODE (dest) == SSA_NAME) { gimple *stmt = SSA_NAME_DEF_STMT (dest); @@ -3287,13 +3282,47 @@ compute_objsize (tree dest, int ostype) if (!is_gimple_assign (stmt)) return NULL_TREE; + dest = gimple_assign_rhs1 (stmt); + tree_code code = gimple_assign_rhs_code (stmt); - if (code != ADDR_EXPR && code != POINTER_PLUS_EXPR) + if (code == POINTER_PLUS_EXPR) + { + /* compute_builtin_object_size fails for addresses with + non-constant offsets. Try to determine the range of + such an offset here and use it to adjus the constant + size. */ + tree off = gimple_assign_rhs2 (stmt); + if (TREE_CODE (off) == SSA_NAME + && INTEGRAL_TYPE_P (TREE_TYPE (off))) + { + wide_int min, max; + enum value_range_type rng = get_range_info (off, &min, &max); + + if (rng == VR_RANGE) + { + if (tree size = compute_objsize (dest, ostype)) + { + wide_int wisiz = wi::to_wide (size); + if (wi::sign_mask (min)) + /* ignore negative offsets for now */; + else if (wi::ltu_p (min, wisiz)) + return wide_int_to_tree (TREE_TYPE (size), + wi::sub (wisiz, min)); + else + return size_zero_node; + } + } + } + } + else if (code != ADDR_EXPR) return NULL_TREE; - - dest = gimple_assign_rhs1 (stmt); } + /* Unless computing the largest size (for memcpy and other raw memory + functions), try to determine the size of the object from its type. */ + if (!ostype) + return NULL_TREE; + if (TREE_CODE (dest) != ADDR_EXPR) return NULL_TREE; Index: gcc/testsuite/gcc.dg/Wstringop-overflow.c =================================================================== --- gcc/testsuite/gcc.dg/Wstringop-overflow.c (nonexistent) +++ gcc/testsuite/gcc.dg/Wstringop-overflow.c (working copy) @@ -0,0 +1,132 @@ +/* PR middle-end/77608 - missing protection on trivially detectable runtime + buffer overflow + { dg-do compile } + { dg-options "-O2 -Wstringop-overflow -ftrack-macro-expansion=0" } */ + +#define SIZE_MAX __SIZE_MAX__ +#define DIFF_MAX __PTRDIFF_MAX__ +#define DIFF_MIN (-DIFF_MAX - 1) + +typedef __SIZE_TYPE__ size_t; + +extern void* memcpy (void*, const void*, size_t); +extern char* strcpy (char*, const char*); +extern char* strncpy (char*, const char*, size_t); + +void sink (void*); + +extern size_t unsigned_value (void) +{ + extern volatile size_t unsigned_value_source; + return unsigned_value_source; +} + +size_t unsigned_range (size_t min, size_t max) +{ + size_t val = unsigned_value (); + return val < min || max < val ? min : val; +} + +#define UR(min, max) unsigned_range (min, max) + + +char a7[7]; + +struct MemArray { char a9[9]; char a1[1]; }; + +void test_memcpy_array (const void *s) +{ +#define T(d, s, n) (memcpy ((d), (s), (n)), sink (d)) + + T (a7 + UR (0, 1), s, 7); + T (a7 + UR (0, 7), s, 7); + T (a7 + UR (0, 8), s, 7); + T (a7 + UR (0, DIFF_MAX), s, 7); + T (a7 + UR (0, SIZE_MAX), s, 7); + + T (a7 + UR (1, 2), s, 7); /* { dg-warning "writing 7 bytes into a region of size 6" } */ + T (a7 + UR (2, 3), s, 7); /* { dg-warning "writing 7 bytes into a region of size 5" } */ + T (a7 + UR (6, 9), s, 7); /* { dg-warning "writing 7 bytes into a region of size 1" } */ + T (a7 + UR (7, 9), s, 7); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + T (a7 + UR (8, 9), s, 7); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + + T (a7 + UR (9, 10), s, 7); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + T (a7 + UR (DIFF_MAX, DIFF_MAX + (size_t)1), s, 7); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + T (a7 + UR (DIFF_MAX, SIZE_MAX), s, 7); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + + /* This is valid. */ + char *d = a7 + 7; + T (d + UR (-8, -7), s, 7); +} + +/* Verify the absence of warnings for memcpy writing beyond object + boundaries. */ + +void test_memcpy_memarray (struct MemArray *p, const void *s) +{ +#undef T +#define T(d, s, n) (memcpy ((d), (s), (n)), sink (d)) + + /* The following are valid. */ + T (p->a9 + UR (0, 1), s, 9); + T (p->a9 + UR (0, 7), s, 9); + T (p->a9 + UR (0, 8), s, 9); + T (p->a9 + UR (0, DIFF_MAX), s, 9); + T (p->a9 + UR (0, SIZE_MAX), s, 9); + + /* The following are invalid. Unfortunately, there is apparently enough + code out there that abuses memcpy to write past the end of one member + and into the members that follow so the following are not diagnosed + by design. It sure would be nice not to have to cater to hacks like + these... */ + T (p->a9 + UR (1, 2), s, 9); + T (p->a9 + UR (1, 2), s, 123); +} + + +void test_strcpy_array (void) +{ +#undef T +#define T(d, s) (strcpy ((d), (s)), sink (d)) + + T (a7 + UR (0, 1), "012345"); + T (a7 + UR (0, 7), "012345"); + T (a7 + UR (0, 8), "012345"); + T (a7 + UR (0, DIFF_MAX), "012345"); + T (a7 + UR (0, SIZE_MAX), "012345"); + + T (a7 + UR (1, 2), "012345"); /* { dg-warning "writing 7 bytes into a region of size 6" } */ + T (a7 + UR (2, 3), "012345"); /* { dg-warning "writing 7 bytes into a region of size 5" } */ + T (a7 + UR (6, 9), "012345"); /* { dg-warning "writing 7 bytes into a region of size 1" } */ + T (a7 + UR (7, 9), "012345"); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + T (a7 + UR (8, 9), "012345"); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + + T (a7 + UR (9, 10), "012345"); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + T (a7 + UR (DIFF_MAX, DIFF_MAX + (size_t)1), "012345"); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + T (a7 + UR (DIFF_MAX, SIZE_MAX), "012345"); /* { dg-warning "writing 7 bytes into a region of size 0" } */ + + char *d = a7 + 7; + + T (d + UR (-8, -7), "012345"); +} + +void test_strncpy_memarray (struct MemArray *p, const void *s) +{ +#undef T +#define T(d, s, n) (strncpy ((d), (s), (n)), sink (d)) + + T (p->a9 + UR (0, 1), s, 9); + T (p->a9 + UR (0, 7), s, 9); + T (p->a9 + UR (0, 8), s, 9); + T (p->a9 + UR (0, DIFF_MAX), s, 9); + T (p->a9 + UR (0, SIZE_MAX), s, 9); + + T (p->a9 + UR (1, 2), s, 9); /* { dg-warning "writing 9 bytes into a region of size 8" } */ + T (p->a9 + UR (2, 3), s, 9); /* { dg-warning "writing 9 bytes into a region of size 7" } */ + T (p->a9 + UR (6, 9), s, 9); /* { dg-warning "writing 9 bytes into a region of size 3" } */ + T (p->a9 + UR (9, 10), s, 9); /* { dg-warning "writing 9 bytes into a region of size 0" } */ + T (p->a9 + UR (10, 11), s, 9); /* { dg-warning "writing 9 bytes into a region of size 0" } */ + + T (p->a9 + UR (DIFF_MAX, DIFF_MAX + (size_t)1), s, 1); /* { dg-warning "writing 1 byte into a region of size 0" } */ + T (p->a9 + UR (DIFF_MAX, SIZE_MAX), s, 3); /* { dg-warning "writing 3 bytes into a region of size 0" } */ +}