From 994477c41049d45b60a4d6db7f624fe5c89860fe Mon Sep 17 00:00:00 2001 From: David Malcolm Date: Thu, 9 May 2024 13:09:29 -0400 Subject: analyzer: fix deref-before-check false positives due to inlining [PR112790] Backported from commit r14-6918-g5743e1899d5964 (moving testcase from c-c++-common to gcc.dg). gcc/analyzer/ChangeLog: PR analyzer/112790 * checker-event.cc (class inlining_info): Move to... * inlining-iterator.h (class inlining_info): ...here. * sm-malloc.cc: Include "analyzer/inlining-iterator.h". (maybe_complain_about_deref_before_check): Reject stmts that were inlined from another function. gcc/testsuite/ChangeLog: PR analyzer/112790 * gcc.dg/analyzer/deref-before-check-pr112790.c: New test. Signed-off-by: David Malcolm --- gcc/analyzer/checker-event.cc | 40 ---------------------- gcc/analyzer/inlining-iterator.h | 40 ++++++++++++++++++++++ gcc/analyzer/sm-malloc.cc | 10 ++++++ .../gcc.dg/analyzer/deref-before-check-pr112790.c | 27 +++++++++++++++ 4 files changed, 77 insertions(+), 40 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr112790.c diff --git a/gcc/analyzer/checker-event.cc b/gcc/analyzer/checker-event.cc index 3612df7..3cb2fb9 100644 --- a/gcc/analyzer/checker-event.cc +++ b/gcc/analyzer/checker-event.cc @@ -106,46 +106,6 @@ event_kind_to_string (enum event_kind ek) } } -/* A class for fixing up fndecls and stack depths in checker_event, based - on inlining records. - - The early inliner runs before the analyzer, which can lead to confusing - output. - - Tne base fndecl and depth within a checker_event are from call strings - in program_points, which reflect the call strings after inlining. - This class lets us offset the depth and fix up the reported fndecl and - stack depth to better reflect the user's original code. */ - -class inlining_info -{ -public: - inlining_info (location_t loc) - { - inlining_iterator iter (loc); - m_inner_fndecl = iter.get_fndecl (); - int num_frames = 0; - while (!iter.done_p ()) - { - m_outer_fndecl = iter.get_fndecl (); - num_frames++; - iter.next (); - } - if (num_frames > 1) - m_extra_frames = num_frames - 1; - else - m_extra_frames = 0; - } - - tree get_inner_fndecl () const { return m_inner_fndecl; } - int get_extra_frames () const { return m_extra_frames; } - -private: - tree m_outer_fndecl; - tree m_inner_fndecl; - int m_extra_frames; -}; - /* class checker_event : public diagnostic_event. */ /* checker_event's ctor. */ diff --git a/gcc/analyzer/inlining-iterator.h b/gcc/analyzer/inlining-iterator.h index 7d4798c..76ba1dc 100644 --- a/gcc/analyzer/inlining-iterator.h +++ b/gcc/analyzer/inlining-iterator.h @@ -106,4 +106,44 @@ private: tree m_next_abstract_origin; }; +/* A class for fixing up fndecls and stack depths in checker_event, based + on inlining records. + + The early inliner runs before the analyzer, which can lead to confusing + output. + + Tne base fndecl and depth within a checker_event are from call strings + in program_points, which reflect the call strings after inlining. + This class lets us offset the depth and fix up the reported fndecl and + stack depth to better reflect the user's original code. */ + +class inlining_info +{ +public: + inlining_info (location_t loc) + { + inlining_iterator iter (loc); + m_inner_fndecl = iter.get_fndecl (); + int num_frames = 0; + while (!iter.done_p ()) + { + m_outer_fndecl = iter.get_fndecl (); + num_frames++; + iter.next (); + } + if (num_frames > 1) + m_extra_frames = num_frames - 1; + else + m_extra_frames = 0; + } + + tree get_inner_fndecl () const { return m_inner_fndecl; } + int get_extra_frames () const { return m_extra_frames; } + +private: + tree m_outer_fndecl; + tree m_inner_fndecl; + int m_extra_frames; +}; + #endif /* GCC_ANALYZER_INLINING_ITERATOR_H */ diff --git a/gcc/analyzer/sm-malloc.cc b/gcc/analyzer/sm-malloc.cc index 7470137..64295cf 100644 --- a/gcc/analyzer/sm-malloc.cc +++ b/gcc/analyzer/sm-malloc.cc @@ -47,6 +47,7 @@ along with GCC; see the file COPYING3. If not see #include "analyzer/program-state.h" #include "analyzer/checker-event.h" #include "analyzer/exploded-graph.h" +#include "analyzer/inlining-iterator.h" #if ENABLE_ANALYZER @@ -2147,6 +2148,15 @@ maybe_complain_about_deref_before_check (sm_context *sm_ctxt, if (checked_in_frame->get_index () > assumed_nonnull_in_frame->get_index ()) return; + /* Don't complain if STMT was inlined from another function, to avoid + similar false positives involving shared helper functions. */ + if (stmt->location) + { + inlining_info info (stmt->location); + if (info.get_extra_frames () > 0) + return; + } + tree diag_ptr = sm_ctxt->get_diagnostic_tree (ptr); if (diag_ptr) sm_ctxt->warn diff --git a/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr112790.c b/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr112790.c new file mode 100644 index 0000000..8f74468 --- /dev/null +++ b/gcc/testsuite/gcc.dg/analyzer/deref-before-check-pr112790.c @@ -0,0 +1,27 @@ +/* Reproducer for false positive from -Wanalyzer-deref-before-check + seen on Linux kernel's block/bdev.c due to -fanalyzer mishandling + inlined functions. */ + +/* { dg-additional-options "-O2 -g -fno-delete-null-pointer-checks" } */ + +typedef unsigned char u8; +struct inode { + void *i_mapping; + u8 i_blkbits; +}; +struct block_device { + struct inode *bd_inode; +}; +int sync_blockdev(struct block_device *bdev); +int set_blocksize(struct block_device *bdev, u8 size) { + if (bdev->bd_inode->i_blkbits != size) { /* { dg-bogus "pointer 'bdev' is dereferenced here" } */ + sync_blockdev(bdev); + } + return 0; +} +extern int filemap_write_and_wait(void *); +int sync_blockdev(struct block_device *bdev) { + if (!bdev) /* { dg-bogus "check of 'bdev' for NULL after already dereferencing it" } */ + return 0; + return filemap_write_and_wait(bdev->bd_inode->i_mapping); +} -- cgit v1.1