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From: Tim Lange <tlange@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2442] analyzer: strcpy semantics Date: Mon, 5 Sep 2022 14:26:05 +0000 (GMT) [thread overview] Message-ID: <20220905142605.35B61385AC2A@sourceware.org> (raw) https://gcc.gnu.org/g:0a9c0d4ae5519c404682425da9522c46c38712fd commit r13-2442-g0a9c0d4ae5519c404682425da9522c46c38712fd Author: Tim Lange <mail@tim-lange.me> Date: Sun Sep 4 21:07:14 2022 +0200 analyzer: strcpy semantics This patch adds modelling for the semantics of strcpy in the simple case where the analyzer is able to infer a concrete string size. Regrtested on Linux x86_64. 2022-09-04 Tim Lange <mail@tim-lange.me> gcc/analyzer/ChangeLog: * region-model-impl-calls.cc (region_model::impl_call_strcpy): Handle the constant string case. * region-model.cc (region_model::get_string_size): New function to get the string size from a region or svalue. * region-model.h (class region_model): Add get_string_size. gcc/testsuite/ChangeLog: * gcc.dg/analyzer/out-of-bounds-4.c: New test. * gcc.dg/analyzer/strcpy-3.c: New test. Diff: --- gcc/analyzer/region-model-impl-calls.cc | 16 ++++-- gcc/analyzer/region-model.cc | 29 +++++++++++ gcc/analyzer/region-model.h | 3 ++ gcc/testsuite/gcc.dg/analyzer/out-of-bounds-4.c | 65 +++++++++++++++++++++++++ gcc/testsuite/gcc.dg/analyzer/strcpy-3.c | 23 +++++++++ 5 files changed, 133 insertions(+), 3 deletions(-) diff --git a/gcc/analyzer/region-model-impl-calls.cc b/gcc/analyzer/region-model-impl-calls.cc index 8eebd122d42..3790eaf2d79 100644 --- a/gcc/analyzer/region-model-impl-calls.cc +++ b/gcc/analyzer/region-model-impl-calls.cc @@ -1019,13 +1019,23 @@ region_model::impl_call_strcpy (const call_details &cd) const svalue *dest_sval = cd.get_arg_svalue (0); const region *dest_reg = deref_rvalue (dest_sval, cd.get_arg_tree (0), cd.get_ctxt ()); + const svalue *src_sval = cd.get_arg_svalue (1); + const region *src_reg = deref_rvalue (src_sval, cd.get_arg_tree (1), + cd.get_ctxt ()); + const svalue *src_contents_sval = get_store_value (src_reg, + cd.get_ctxt ()); cd.maybe_set_lhs (dest_sval); - check_region_for_write (dest_reg, cd.get_ctxt ()); + /* Try to get the string size if SRC_REG is a string_region. */ + const svalue *copied_bytes_sval = get_string_size (src_reg); + /* Otherwise, check if the contents of SRC_REG is a string. */ + if (copied_bytes_sval->get_kind () == SK_UNKNOWN) + copied_bytes_sval = get_string_size (src_contents_sval); - /* For now, just mark region's contents as unknown. */ - mark_region_as_unknown (dest_reg, cd.get_uncertainty ()); + const region *sized_dest_reg + = m_mgr->get_sized_region (dest_reg, NULL_TREE, copied_bytes_sval); + set_value (sized_dest_reg, src_contents_sval, cd.get_ctxt ()); } /* Handle the on_call_pre part of "strlen". */ diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc index 5a64c00ef14..e84087abc1f 100644 --- a/gcc/analyzer/region-model.cc +++ b/gcc/analyzer/region-model.cc @@ -3218,6 +3218,35 @@ region_model::get_capacity (const region *reg) const return m_mgr->get_or_create_unknown_svalue (sizetype); } +/* Return the string size, including the 0-terminator, if SVAL is a + constant_svalue holding a string. Otherwise, return an unknown_svalue. */ + +const svalue * +region_model::get_string_size (const svalue *sval) const +{ + tree cst = sval->maybe_get_constant (); + if (!cst || TREE_CODE (cst) != STRING_CST) + return m_mgr->get_or_create_unknown_svalue (size_type_node); + + tree out = build_int_cst (size_type_node, TREE_STRING_LENGTH (cst)); + return m_mgr->get_or_create_constant_svalue (out); +} + +/* Return the string size, including the 0-terminator, if REG is a + string_region. Otherwise, return an unknown_svalue. */ + +const svalue * +region_model::get_string_size (const region *reg) const +{ + const string_region *str_reg = dyn_cast <const string_region *> (reg); + if (!str_reg) + return m_mgr->get_or_create_unknown_svalue (size_type_node); + + tree cst = str_reg->get_string_cst (); + tree out = build_int_cst (size_type_node, TREE_STRING_LENGTH (cst)); + return m_mgr->get_or_create_constant_svalue (out); +} + /* If CTXT is non-NULL, use it to warn about any problems accessing REG, using DIR to determine if this access is a read or write. */ diff --git a/gcc/analyzer/region-model.h b/gcc/analyzer/region-model.h index 7ce832f6ce4..a1f2165e145 100644 --- a/gcc/analyzer/region-model.h +++ b/gcc/analyzer/region-model.h @@ -793,6 +793,9 @@ class region_model const svalue *get_capacity (const region *reg) const; + const svalue *get_string_size (const svalue *sval) const; + const svalue *get_string_size (const region *reg) const; + /* Implemented in sm-malloc.cc */ void on_realloc_with_move (const call_details &cd, const svalue *old_ptr_sval, diff --git a/gcc/testsuite/gcc.dg/analyzer/out-of-bounds-4.c b/gcc/testsuite/gcc.dg/analyzer/out-of-bounds-4.c new file mode 100644 index 00000000000..46f600de658 --- /dev/null +++ b/gcc/testsuite/gcc.dg/analyzer/out-of-bounds-4.c @@ -0,0 +1,65 @@ +/* { dg-additional-options "-Wno-stringop-overflow -Wno-stringop-truncation" } */ +#include <string.h> + +/* Wanalyzer-out-of-bounds tests for strpy-related overflows. + + The intra-procedural tests are all caught by Wstringop-overflow. + The inter-procedural out-of-bounds are only found by the analyzer. */ + +void test1 (void) +{ + char dst[5]; + strcpy (dst, "Hello"); /* { dg-line test1 } */ + + /* { dg-warning "overflow" "warning" { target *-*-* } test1 } */ + /* { dg-message "dst" "note" { target *-*-* } test1 } */ +} + +void test2 (void) +{ + char dst[6]; + strcpy (dst, "Hello"); +} + +void test3 (void) +{ + char *src = "Hello"; + char dst[5]; + strcpy (dst, src); /* { dg-line test3 } */ + + /* { dg-warning "overflow" "warning" { target *-*-* } test3 } */ + /* { dg-message "dst" "note" { target *-*-* } test3 } */ +} + +void test4 (void) +{ + char *src = "Hello"; + char dst[6]; + strcpy (dst, src); +} + +const char *return_hello (void) +{ + return "hello"; +} + +void test5 (void) +{ + const char *str = return_hello (); + if (!str) + return; + char dst[5]; + strcpy (dst, str); /* { dg-line test5 } */ + + /* { dg-warning "overflow" "warning" { target *-*-* } test5 } */ + /* { dg-message "dst" "note" { target *-*-* } test5 } */ +} + +void test6 (void) +{ + const char *str = return_hello (); + if (!str) + return; + char dst[6]; + strcpy (dst, str); +} diff --git a/gcc/testsuite/gcc.dg/analyzer/strcpy-3.c b/gcc/testsuite/gcc.dg/analyzer/strcpy-3.c new file mode 100644 index 00000000000..a38f9a7641f --- /dev/null +++ b/gcc/testsuite/gcc.dg/analyzer/strcpy-3.c @@ -0,0 +1,23 @@ +#include <string.h> +#include "analyzer-decls.h" + +void test_1 (void) +{ + char str[] = "Hello"; + char buf[6]; + char *result = strcpy (buf, str); + __analyzer_describe (1, result); /* { dg-warning "region_svalue.*?'buf'" } */ + __analyzer_eval (result == buf); /* { dg-warning "TRUE" } */ + __analyzer_eval (buf[0] == 'H'); /* { dg-warning "TRUE" } */ + __analyzer_eval (buf[1] == 'e'); /* { dg-warning "TRUE" } */ + __analyzer_eval (buf[2] == 'l'); /* { dg-warning "TRUE" } */ + __analyzer_eval (buf[3] == 'l'); /* { dg-warning "TRUE" } */ + __analyzer_eval (buf[4] == 'o'); /* { dg-warning "TRUE" } */ + __analyzer_eval (buf[5] == 0); /* { dg-warning "TRUE" } */ + __analyzer_eval (result[0] == 'H'); /* { dg-warning "TRUE" } */ + __analyzer_eval (result[1] == 'e'); /* { dg-warning "TRUE" } */ + __analyzer_eval (result[2] == 'l'); /* { dg-warning "TRUE" } */ + __analyzer_eval (result[3] == 'l'); /* { dg-warning "TRUE" } */ + __analyzer_eval (result[4] == 'o'); /* { dg-warning "TRUE" } */ + __analyzer_eval (result[5] == 0); /* { dg-warning "TRUE" } */ +}
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