From e1a9168153d2bf12695844a9ca9f9fc1de8d1ddf Mon Sep 17 00:00:00 2001 From: David Malcolm Date: Fri, 5 Aug 2022 19:45:41 -0400 Subject: [PATCH] New warning: -Wanalyzer-jump-through-null [PR105947] This patch adds a new warning to -fanalyzer for jumps through NULL function pointers. gcc/analyzer/ChangeLog: PR analyzer/105947 * analyzer.opt (Wanalyzer-jump-through-null): New option. * engine.cc (class jump_through_null): New. (exploded_graph::process_node): Complain about jumps through NULL function pointers. gcc/ChangeLog: PR analyzer/105947 * doc/invoke.texi: Add -Wanalyzer-jump-through-null. gcc/testsuite/ChangeLog: PR analyzer/105947 * gcc.dg/analyzer/function-ptr-5.c: New test. Signed-off-by: David Malcolm --- gcc/analyzer/analyzer.opt | 4 +++ gcc/analyzer/engine.cc | 49 ++++++++++++++++++++++++++ gcc/doc/invoke.texi | 12 +++++++ gcc/testsuite/gcc.dg/analyzer/function-ptr-5.c | 42 ++++++++++++++++++++++ 4 files changed, 107 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/analyzer/function-ptr-5.c diff --git a/gcc/analyzer/analyzer.opt b/gcc/analyzer/analyzer.opt index 808ff36..c6d9c53 100644 --- a/gcc/analyzer/analyzer.opt +++ b/gcc/analyzer/analyzer.opt @@ -98,6 +98,10 @@ Wanalyzer-free-of-non-heap Common Var(warn_analyzer_free_of_non_heap) Init(1) Warning Warn about code paths in which a non-heap pointer is freed. +Wanalyzer-jump-through-null +Common Var(warn_analyzer_jump_through_null) Init(1) Warning +Warn about code paths in which a NULL function pointer is called. + Wanalyzer-malloc-leak Common Var(warn_analyzer_malloc_leak) Init(1) Warning Warn about code paths in which a heap-allocated pointer leaks. diff --git a/gcc/analyzer/engine.cc b/gcc/analyzer/engine.cc index 85b7c5e..e8db00d 100644 --- a/gcc/analyzer/engine.cc +++ b/gcc/analyzer/engine.cc @@ -3705,6 +3705,46 @@ private: bool m_terminate_path; }; +/* A subclass of pending_diagnostic for complaining about jumps through NULL + function pointers. */ + +class jump_through_null : public pending_diagnostic_subclass +{ +public: + jump_through_null (const gcall *call) + : m_call (call) + {} + + const char *get_kind () const final override + { + return "jump_through_null"; + } + + bool operator== (const jump_through_null &other) const + { + return m_call == other.m_call; + } + + int get_controlling_option () const final override + { + return OPT_Wanalyzer_jump_through_null; + } + + bool emit (rich_location *rich_loc) final override + { + return warning_at (rich_loc, get_controlling_option (), + "jump through null pointer"); + } + + label_text describe_final_event (const evdesc::final_event &ev) final override + { + return ev.formatted_print ("jump through null pointer here"); + } + +private: + const gcall *m_call; +}; + /* The core of exploded_graph::process_worklist (the main analysis loop), handling one node in the worklist. @@ -4046,6 +4086,15 @@ exploded_graph::process_node (exploded_node *node) logger); if (!call_discovered) { + /* Check for jump through NULL. */ + if (tree fn_ptr = gimple_call_fn (call)) + { + const svalue *fn_ptr_sval + = model->get_rvalue (fn_ptr, &ctxt); + if (fn_ptr_sval->all_zeroes_p ()) + ctxt.warn (new jump_through_null (call)); + } + /* An unknown function or a special function was called at this point, in such case, don't terminate the analysis of the current function. diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 863580b..92f7aae 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -453,6 +453,7 @@ Objective-C and Objective-C++ Dialects}. -Wno-analyzer-fd-use-without-check @gol -Wno-analyzer-file-leak @gol -Wno-analyzer-free-of-non-heap @gol +-Wno-analyzer-jump-through-null @gol -Wno-analyzer-malloc-leak @gol -Wno-analyzer-mismatching-deallocation @gol -Wno-analyzer-null-argument @gol @@ -9756,6 +9757,7 @@ Enabling this option effectively enables the following warnings: -Wanalyzer-fd-use-without-check @gol -Wanalyzer-file-leak @gol -Wanalyzer-free-of-non-heap @gol +-Wanalyzer-jump-through-null @gol -Wanalyzer-malloc-leak @gol -Wanalyzer-mismatching-deallocation @gol -Wanalyzer-null-argument @gol @@ -9942,6 +9944,16 @@ is called on a non-heap pointer (e.g. an on-stack buffer, or a global). See @uref{https://cwe.mitre.org/data/definitions/590.html, CWE-590: Free of Memory not on the Heap}. +@item -Wno-analyzer-jump-through-null +@opindex Wanalyzer-jump-through-null +@opindex Wno-analyzer-jump-through-null +This warning requires @option{-fanalyzer}, which enables it; use +@option{-Wno-analyzer-jump-through-null} +to disable it. + +This diagnostic warns for paths through the code in which a @code{NULL} +function pointer is called. + @item -Wno-analyzer-malloc-leak @opindex Wanalyzer-malloc-leak @opindex Wno-analyzer-malloc-leak diff --git a/gcc/testsuite/gcc.dg/analyzer/function-ptr-5.c b/gcc/testsuite/gcc.dg/analyzer/function-ptr-5.c new file mode 100644 index 0000000..3c46f28 --- /dev/null +++ b/gcc/testsuite/gcc.dg/analyzer/function-ptr-5.c @@ -0,0 +1,42 @@ +#define NULL ((void *)0) + +void calling_null_fn_ptr_1 (void) +{ + void (*fn_ptr) (void) = NULL; + fn_ptr (); /* { dg-warning "jump through null pointer" } */ +} + +int calling_null_fn_ptr_2 (void) +{ + int (*fn_ptr) (void) = NULL; + return fn_ptr (); /* { dg-warning "jump through null pointer" } */ +} + +typedef void (*void_void_fn_ptr) (void); + +void calling_const_fn_ptr (void) +{ + void_void_fn_ptr fn_ptr = (void_void_fn_ptr)0xffd2; + return fn_ptr (); +} + +void skipping_init (int flag) +{ + void_void_fn_ptr fn_ptr = NULL; + if (flag) /* { dg-message "branch" } */ + fn_ptr = (void_void_fn_ptr)0xffd2; + fn_ptr (); /* { dg-warning "jump through null pointer" } */ +} + +struct callbacks +{ + void_void_fn_ptr on_redraw; + void_void_fn_ptr on_cleanup; +}; + +void test_callbacks (void) +{ + struct callbacks cb; + __builtin_memset (&cb, 0, sizeof (cb)); + cb.on_cleanup (); /* { dg-warning "jump through null pointer" } */ +} -- 2.7.4