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analyzer: fixes to memcpy [PR103872]

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PR analyzer/103872 reports a failure of gcc.dg/analyzer/pr103526.c on
riscv64-unknown-elf-gcc.  The issue is that I wrote the test on x86_64
where a memcpy in the test is optimized to a write to a read/write pair,
whereas due to alignment differences the analyzer can see it as a
memcpy call, revealing problems with the analyzer's implementation
of memcpy.

This patch reimplements region_model::impl_call_memcpy in terms of a
get_store_value followed by a set_value, fixing the issue.

gcc/analyzer/ChangeLog:
	PR analyzer/103872
	* region-model-impl-calls.cc (region_model::impl_call_memcpy):
	Reimplement in terms of a get_store_value followed by a set_value.

gcc/testsuite/ChangeLog:
	PR analyzer/103872
	* gcc.dg/analyzer/memcpy-1.c: Add alternate versions of test cases
	in which the calls to memcpy are hidden from the optimizer.  Add
	further test cases.
	* gcc.dg/analyzer/taint-size-1.c: Add test coverage for memcpy
	with tainted size.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>
This commit is contained in:
David Malcolm 2022-02-03 16:21:27 -05:00
parent f30e65e94d
commit 9d2c0fad59
3 changed files with 148 additions and 14 deletions
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28
gcc/analyzer/region-model-impl-calls.cc
View File

@ -491,29 +491,29 @@ region_model::impl_call_malloc (const call_details &cd)
}
/* Handle the on_call_pre part of "memcpy" and "__builtin_memcpy". */
// TODO: complain about overlapping src and dest.
void
region_model::impl_call_memcpy (const call_details &cd)
{
const svalue *dest_sval = cd.get_arg_svalue (0);
const svalue *dest_ptr_sval = cd.get_arg_svalue (0);
const svalue *src_ptr_sval = cd.get_arg_svalue (1);
const svalue *num_bytes_sval = cd.get_arg_svalue (2);
const region *dest_reg = deref_rvalue (dest_sval, cd.get_arg_tree (0),
const region *dest_reg = deref_rvalue (dest_ptr_sval, cd.get_arg_tree (0),
cd.get_ctxt ());
const region *src_reg = deref_rvalue (src_ptr_sval, cd.get_arg_tree (1),
cd.get_ctxt ());
cd.maybe_set_lhs (dest_sval);
cd.maybe_set_lhs (dest_ptr_sval);
if (tree num_bytes = num_bytes_sval->maybe_get_constant ())
{
/* "memcpy" of zero size is a no-op. */
if (zerop (num_bytes))
return;
}
check_region_for_write (dest_reg, cd.get_ctxt ());
/* Otherwise, mark region's contents as unknown. */
mark_region_as_unknown (dest_reg, cd.get_uncertainty ());
const region *sized_src_reg
= m_mgr->get_sized_region (src_reg, NULL_TREE, num_bytes_sval);
const region *sized_dest_reg
= m_mgr->get_sized_region (dest_reg, NULL_TREE, num_bytes_sval);
const svalue *src_contents_sval
= get_store_value (sized_src_reg, cd.get_ctxt ());
set_value (sized_dest_reg, src_contents_sval, cd.get_ctxt ());
}
/* Handle the on_call_pre part of "memset" and "__builtin_memset". */

125
gcc/testsuite/gcc.dg/analyzer/memcpy-1.c
View File

@ -1,6 +1,16 @@
#include <string.h>
#include "analyzer-decls.h"
/* Function for thwarting expansion of memcpy by optimizer. */
typedef void * (*memcpy_t) (void *dst, const void *src, size_t n);
static memcpy_t __attribute__((noinline))
get_memcpy (void)
{
return memcpy;
}
void *test_1 (void *dst, void *src, size_t n)
{
void *result = memcpy (dst, src, n);
@ -15,6 +25,14 @@ void *test_1a (void *dst, void *src, size_t n)
return result;
}
void *test_1b (void *dst, void *src, size_t n)
{
memcpy_t fn = get_memcpy ();
void *result = fn (dst, src, n);
__analyzer_eval (result == dst); /* { dg-warning "TRUE" } */
return result;
}
void test_2 (int i)
{
int j;
@ -29,6 +47,14 @@ void test_2a (int i)
__analyzer_eval (i == j); /* { dg-warning "TRUE" } */
}
void test_2b (int i)
{
int j;
memcpy_t fn = get_memcpy ();
fn (&j, &i, sizeof (int));
__analyzer_eval (i == j); /* { dg-warning "TRUE" } */
}
void test_3 (void *src, size_t n)
{
char buf[40], other[40];
@ -41,3 +67,102 @@ void test_3 (void *src, size_t n)
__analyzer_eval (buf[0] == 'a'); /* { dg-warning "UNKNOWN" } */
__analyzer_eval (other[0] == 'b'); /* { dg-warning "TRUE" } */
}
void test_3b (void *src, size_t n)
{
char buf[40], other[40];
memcpy_t fn = get_memcpy ();
buf[0] = 'a';
other[0] = 'b';
__analyzer_eval (buf[0] == 'a'); /* { dg-warning "TRUE" } */
__analyzer_eval (other[0] == 'b'); /* { dg-warning "TRUE" } */
fn (buf, src, n);
__analyzer_eval (buf[0] == 'a'); /* { dg-warning "UNKNOWN" } */
__analyzer_eval (other[0] == 'b'); /* { dg-warning "TRUE" } */
}
/* Overwriting a zeroed buffer, then memcpy of the result. */
void test_4 (int a, int b)
{
int src[1024];
int dst[1024];
memset (src, 0, sizeof (src));
src[42] = a;
src[100] = b;
__analyzer_eval (src[0] == 0); /* { dg-warning "TRUE" } */
__analyzer_eval (src[42] == a); /* { dg-warning "TRUE" } */
__analyzer_eval (src[100] == b); /* { dg-warning "TRUE" } */
__analyzer_eval (src[1023] == 0); /* { dg-warning "TRUE" } */
memcpy (dst, src, sizeof (src));
__analyzer_eval (dst[0] == 0); /* { dg-warning "TRUE" } */
__analyzer_eval (dst[42] == a); /* { dg-warning "TRUE" } */
__analyzer_eval (dst[100] == b); /* { dg-warning "TRUE" } */
__analyzer_eval (dst[1023] == 0); /* { dg-warning "TRUE" } */
}
void test_4b (int a, int b)
{
int src[1024];
int dst[1024];
memcpy_t fn = get_memcpy ();
memset (src, 0, sizeof (src));
src[42] = a;
src[100] = b;
__analyzer_eval (src[0] == 0); /* { dg-warning "TRUE" } */
__analyzer_eval (src[42] == a); /* { dg-warning "TRUE" } */
__analyzer_eval (src[100] == b); /* { dg-warning "TRUE" } */
__analyzer_eval (src[1023] == 0); /* { dg-warning "TRUE" } */
fn (dst, src, sizeof (src));
__analyzer_eval (dst[0] == 0); /* { dg-warning "TRUE" } */
__analyzer_eval (dst[42] == a); /* { dg-warning "TRUE" } */
__analyzer_eval (dst[100] == b); /* { dg-warning "TRUE" } */
__analyzer_eval (dst[1023] == 0); /* { dg-warning "TRUE" } */
}
/* Populating a buffer from an unknown buffer. */
void test_5 (void *src, size_t sz)
{
char dst[1024];
memcpy (dst, src, sizeof (dst));
__analyzer_eval (dst[0] == 0); /* { dg-warning "UNKNOWN" } */
__analyzer_eval (dst[1023] == 0); /* { dg-warning "UNKNOWN" } */
}
void test_5b (void *src, size_t sz)
{
char dst[1024];
memcpy_t fn = get_memcpy ();
fn (dst, src, sizeof (dst));
__analyzer_eval (dst[0] == 0); /* { dg-warning "UNKNOWN" } */
__analyzer_eval (dst[1023] == 0); /* { dg-warning "UNKNOWN" } */
}
/* Zero-sized memcpy. */
void test_6 (void *dst, void *src)
{
memcpy (dst, src, 0);
}
void test_6b (void *dst, void *src)
{
memcpy_t fn = get_memcpy ();
fn (dst, src, 0);
}
/* memcpy to string literal. */
void test_7 (void *src, size_t sz)
{
memcpy ((void *)"hello world", src, sz); /* { dg-warning "write to string literal" } */
}
void test_7b (void *src, size_t sz)
{
memcpy ((void *)"hello world", src, sz); /* { dg-warning "write to string literal" } */
}

9
gcc/testsuite/gcc.dg/analyzer/taint-size-1.c
View File

@ -12,6 +12,7 @@ struct foo
};
char buf[100];
char buf2[100];
/* memset with tainted size. */
@ -30,3 +31,11 @@ void test_1 (FILE *f)
// TOOD: better messages for state changes
}
}
/* memcpy with tainted size. */
void __attribute__((tainted_args))
test_2 (size_t sz)
{
memcpy (buf, buf2, sz); /* { dg-warning "use of attacker-controlled value 'sz' as size without upper-bounds checking" } */
}