[gcc r14-8428] analyzer: fix defaults in compound assignments from non-zero offsets [PR112969]

[David Malcolm <dmalcolm@gcc.gnu.org>]

https://gcc.gnu.org/g:6426d466779fa889bca170e3ff80dbfc6ea8c2e8

commit r14-8428-g6426d466779fa889bca170e3ff80dbfc6ea8c2e8
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Thu Jan 25 10:06:12 2024 -0500

    analyzer: fix defaults in compound assignments from non-zero offsets [PR112969]
    
    Confusion in binding_cluster::maybe_get_compound_binding about whether
    offsets are relative to the start of the region or to the start of the
    cluster was leading to incorrect handling of default values, leading
    to false positives from -Wanalyzer-use-of-uninitialized-value, from
    -Wanalyzer-exposure-through-uninit-copy, and other logic errors.
    
    Fixed thusly.
    
    gcc/analyzer/ChangeLog:
            PR analyzer/112969
            * store.cc (binding_cluster::maybe_get_compound_binding): When
            populating default_map, express the bit-range of the default key
            for REG relative to REG, rather than to the base region.
    
    gcc/testsuite/ChangeLog:
            PR analyzer/112969
            * c-c++-common/analyzer/compound-assignment-5.c (test_3): Remove
            xfails, reorder tests.
            * c-c++-common/analyzer/compound-assignment-pr112969.c: New test.
            * gcc.dg/plugin/infoleak-pr112969.c: New test.
            * gcc.dg/plugin/plugin.exp: Add infoleak-pr112969.c to
            analyzer_kernel_plugin.c tests.
    
    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

Diff:
---
 gcc/analyzer/store.cc                              | 11 ++++-
 .../c-c++-common/analyzer/compound-assignment-5.c  |  3 +-
 .../analyzer/compound-assignment-pr112969.c        | 35 +++++++++++++++
 gcc/testsuite/gcc.dg/plugin/infoleak-pr112969.c    | 52 ++++++++++++++++++++++
 gcc/testsuite/gcc.dg/plugin/plugin.exp             |  1 +
 5 files changed, 99 insertions(+), 3 deletions(-)

diff --git a/gcc/analyzer/store.cc b/gcc/analyzer/store.cc
index 67c90b7fce4a..e85a19647f7e 100644
--- a/gcc/analyzer/store.cc
+++ b/gcc/analyzer/store.cc
@@ -1759,7 +1759,16 @@ binding_cluster::maybe_get_compound_binding (store_manager *mgr,
   else
     default_sval = sval_mgr->get_or_create_initial_value (reg);
   const binding_key *default_key = binding_key::make (mgr, reg);
-  default_map.put (default_key, default_sval);
+
+  /* Express the bit-range of the default key for REG relative to REG,
+     rather than to the base region.  */
+  const concrete_binding *concrete_default_key
+    = default_key->dyn_cast_concrete_binding ();
+  if (!concrete_default_key)
+    return nullptr;
+  const concrete_binding *default_key_relative_to_reg
+     = mgr->get_concrete_binding (0, concrete_default_key->get_size_in_bits ());
+  default_map.put (default_key_relative_to_reg, default_sval);
 
   for (map_t::iterator iter = m_map.begin (); iter != m_map.end (); ++iter)
     {
diff --git a/gcc/testsuite/c-c++-common/analyzer/compound-assignment-5.c b/gcc/testsuite/c-c++-common/analyzer/compound-assignment-5.c
index 3ce2b72c8ff3..08f10606d91f 100644
--- a/gcc/testsuite/c-c++-common/analyzer/compound-assignment-5.c
+++ b/gcc/testsuite/c-c++-common/analyzer/compound-assignment-5.c
@@ -48,9 +48,8 @@ void test_3 (void)
 
   glob_arr3[7] = arr[3]; // or should the uninit warning be here?
 
-  __analyzer_eval (glob_arr3[7].x); /* { dg-warning "uninitialized" "uninit" { xfail *-*-* } } */
-  /* { dg-bogus "UNKNOWN" "unknown" { xfail *-*-* } .-1 } */
   __analyzer_eval (glob_arr3[7].y == 6); /* { dg-warning "TRUE" } */
+  __analyzer_eval (glob_arr3[7].x); /* { dg-warning "uninitialized" "uninit" } */
 }
 
 /* Symbolic bindings: copying from one array to another.  */
diff --git a/gcc/testsuite/c-c++-common/analyzer/compound-assignment-pr112969.c b/gcc/testsuite/c-c++-common/analyzer/compound-assignment-pr112969.c
new file mode 100644
index 000000000000..4bc037cb7cfc
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/analyzer/compound-assignment-pr112969.c
@@ -0,0 +1,35 @@
+/* Reduced from -Wanalyzer-exposure-through-uninit-copy false positives
+   seen in Linux kernel in drivers/net/ethernet/intel/ice/ice_ptp.c  */
+
+#include "analyzer-decls.h"
+
+/* { dg-do compile } */
+
+struct hwtstamp_config
+{
+  int flags;
+  int tx_type;
+  int rx_filter;
+};
+
+struct ice_ptp
+{
+  long placeholder;
+  struct hwtstamp_config tstamp_config;
+};
+
+struct ice_pf
+{
+  struct ice_ptp ptp;
+};
+
+void
+ice_ptp_set_ts_config(struct ice_pf* pf)
+{
+  struct hwtstamp_config config;
+  pf->ptp.tstamp_config.tx_type = 1;
+  pf->ptp.tstamp_config.rx_filter = 2;
+  config = pf->ptp.tstamp_config;
+  __analyzer_eval (config.flags == pf->ptp.tstamp_config.flags); /* { dg-warning "TRUE" } */
+  /* { dg-bogus "use of uninitialized value 'config.flags'" "PR analyzer/112969" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/gcc.dg/plugin/infoleak-pr112969.c b/gcc/testsuite/gcc.dg/plugin/infoleak-pr112969.c
new file mode 100644
index 000000000000..e78fe3659759
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/plugin/infoleak-pr112969.c
@@ -0,0 +1,52 @@
+/* Reduced from -Wanalyzer-exposure-through-uninit-copy false positives
+   seen in Linux kernel in drivers/net/ethernet/intel/ice/ice_ptp.c  */
+
+/* { dg-do compile } */
+/* { dg-options "-fanalyzer" } */
+/* { dg-require-effective-target analyzer } */
+
+extern unsigned long
+copy_from_user(void* to, const void* from, unsigned long n);
+
+extern unsigned long
+copy_to_user(void* to, const void* from, unsigned long n);
+
+struct ifreq
+{
+  union
+  {
+    void* ifru_data;
+  } ifr_ifru;
+};
+
+struct hwtstamp_config
+{
+  int flags;
+  int tx_type;
+  int rx_filter;
+};
+
+struct ice_ptp
+{
+  long placeholder;
+  struct hwtstamp_config tstamp_config;
+};
+
+struct ice_pf
+{
+  struct ice_ptp ptp;
+};
+int
+ice_ptp_set_ts_config(struct ice_pf* pf, struct ifreq* ifr)
+{
+  struct hwtstamp_config config;
+  int err;
+  if (copy_from_user(&config, ifr->ifr_ifru.ifru_data, sizeof(config)))
+    return -14;
+  pf->ptp.tstamp_config.tx_type = 0;
+  pf->ptp.tstamp_config.rx_filter = 0;
+  config = pf->ptp.tstamp_config;
+  if (copy_to_user(ifr->ifr_ifru.ifru_data, &config, sizeof(config))) /* { dg-bogus "-Wanalyzer-exposure-through-uninit-copy" "PR analyzer/112969" } */
+    return -14;
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/plugin/plugin.exp b/gcc/testsuite/gcc.dg/plugin/plugin.exp
index 8141cc2aa46d..c26dda1f324b 100644
--- a/gcc/testsuite/gcc.dg/plugin/plugin.exp
+++ b/gcc/testsuite/gcc.dg/plugin/plugin.exp
@@ -150,6 +150,7 @@ set plugin_test_list [list \
 	  infoleak-CVE-2017-18550-1.c \
 	  infoleak-antipatterns-1.c \
 	  infoleak-fixit-1.c \
+	  infoleak-pr112969.c \
 	  infoleak-uninit-size-1.c \
 	  infoleak-uninit-size-2.c \
 	  infoleak-net-ethtool-ioctl.c \