Re: PING^2 (C/C++): Re: [PATCH 6/6] Add __attribute__ ((tainted))

[Jason Merrill <jason@redhat.com>]

On 1/10/22 16:36, David Malcolm via Gcc-patches wrote:
> On Thu, 2022-01-06 at 09:08 -0500, David Malcolm wrote:
>> On Sat, 2021-11-13 at 15:37 -0500, David Malcolm wrote:
>>> This patch adds a new __attribute__ ((tainted)) to the C/C++
>>> frontends.
>>
>> Ping for GCC C/C++ mantainers for review of the C/C++ FE parts of this
>> patch (attribute registration, documentation, the name of the
>> attribute, etc).
>>
>> (I believe it's independent of the rest of the patch kit, in that it
>> could go into trunk without needing the prior patches)
>>
>> Thanks
>> Dave
> 
> Getting close to end of stage 3 for GCC 12, so pinging this patch
> again...
> 
> https://gcc.gnu.org/pipermail/gcc-patches/2021-November/584376.html

The c-family change is OK.

> Thanks
> Dave
> 
>>
>>
>>>
>>> It can be used on function decls: the analyzer will treat as tainted
>>> all parameters to the function and all buffers pointed to by
>>> parameters
>>> to the function.  Adding this in one place to the Linux kernel's
>>> __SYSCALL_DEFINEx macro allows the analyzer to treat all syscalls as
>>> having tainted inputs.  This gives additional testing beyond e.g.
>>> __user
>>> pointers added by earlier patches - an example of the use of this can
>>> be
>>> seen in CVE-2011-2210, where given:
>>>
>>>   SYSCALL_DEFINE5(osf_getsysinfo, unsigned long, op, void __user *,
>>> buffer,
>>>                   unsigned long, nbytes, int __user *, start, void
>>> __user *, arg)
>>>
>>> the analyzer will treat the nbytes param as under attacker control,
>>> and
>>> can complain accordingly:
>>>
>>> taint-CVE-2011-2210-1.c: In function ‘sys_osf_getsysinfo’:
>>> taint-CVE-2011-2210-1.c:69:21: warning: use of attacker-controlled
>>> value
>>>    ‘nbytes’ as size without upper-bounds checking [CWE-129] [-
>>> Wanalyzer-tainted-size]
>>>     69 |                 if (copy_to_user(buffer, hwrpb, nbytes) != 0)
>>>        |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Additionally, the patch allows the attribute to be used on field
>>> decls:
>>> specifically function pointers.  Any function used as an initializer
>>> for such a field gets treated as tainted.  An example can be seen in
>>> CVE-2020-13143, where adding __attribute__((tainted)) to the "store"
>>> callback of configfs_attribute:
>>>
>>>    struct configfs_attribute {
>>>       /* [...snip...] */
>>>       ssize_t (*store)(struct config_item *, const char *, size_t)
>>>         __attribute__((tainted));
>>>       /* [...snip...] */
>>>    };
>>>
>>> allows the analyzer to see:
>>>
>>>   CONFIGFS_ATTR(gadget_dev_desc_, UDC);
>>>
>>> and treat gadget_dev_desc_UDC_store as tainted, so that it complains:
>>>
>>> taint-CVE-2020-13143-1.c: In function ‘gadget_dev_desc_UDC_store’:
>>> taint-CVE-2020-13143-1.c:33:17: warning: use of attacker-controlled
>>> value
>>>    ‘len + 18446744073709551615’ as offset without upper-bounds
>>> checking [CWE-823] [-Wanalyzer-tainted-offset]
>>>     33 |         if (name[len - 1] == '\n')
>>>        |             ~~~~^~~~~~~~~
>>>
>>> Similarly, the attribute could be used on the ioctl callback field,
>>> USB device callbacks, network-handling callbacks etc.  This
>>> potentially
>>> gives a lot of test coverage with relatively little code annotation,
>>> and
>>> without necessarily needing link-time analysis (which -fanalyzer can
>>> only do at present on trivial examples).
>>>
>>> I believe this is the first time we've had an attribute on a field.
>>> If that's an issue, I could prepare a version of the patch that
>>> merely allowed it on functions themselves.
>>>
>>> As before this currently still needs -fanalyzer-checker=taint (in
>>> addition to -fanalyzer).
>>>
>>> gcc/analyzer/ChangeLog:
>>>          * engine.cc: Include "stringpool.h", "attribs.h", and
>>>          "tree-dfa.h".
>>>          (mark_params_as_tainted): New.
>>>          (class tainted_function_custom_event): New.
>>>          (class tainted_function_info): New.
>>>          (exploded_graph::add_function_entry): Handle functions with
>>>          "tainted" attribute.
>>>          (class tainted_field_custom_event): New.
>>>          (class tainted_callback_custom_event): New.
>>>          (class tainted_call_info): New.
>>>          (add_tainted_callback): New.
>>>          (add_any_callbacks): New.
>>>          (exploded_graph::build_initial_worklist): Find callbacks that
>>> are
>>>          reachable from global initializers, calling add_any_callbacks
>>> on
>>>          them.
>>>
>>> gcc/c-family/ChangeLog:
>>>          * c-attribs.c (c_common_attribute_table): Add "tainted".
>>>          (handle_tainted_attribute): New.
>>>
>>> gcc/ChangeLog:
>>>          * doc/extend.texi (Function Attributes): Note that "tainted"
>>> can
>>>          be used on field decls.
>>>          (Common Function Attributes): Add entry on "tainted"
>>> attribute.
>>>
>>> gcc/testsuite/ChangeLog:
>>>          * gcc.dg/analyzer/attr-tainted-1.c: New test.
>>>          * gcc.dg/analyzer/attr-tainted-misuses.c: New test.
>>>          * gcc.dg/analyzer/taint-CVE-2011-2210-1.c: New test.
>>>          * gcc.dg/analyzer/taint-CVE-2020-13143-1.c: New test.
>>>          * gcc.dg/analyzer/taint-CVE-2020-13143-2.c: New test.
>>>          * gcc.dg/analyzer/taint-CVE-2020-13143.h: New test.
>>>          * gcc.dg/analyzer/taint-alloc-3.c: New test.
>>>          * gcc.dg/analyzer/taint-alloc-4.c: New test.
>>>
>>> Signed-off-by: David Malcolm <dmalcolm@redhat.com>
>>> ---
>>>   gcc/analyzer/engine.cc                        | 317
>>> +++++++++++++++++-
>>>   gcc/c-family/c-attribs.c                      |  36 ++
>>>   gcc/doc/extend.texi                           |  22 +-
>>>   .../gcc.dg/analyzer/attr-tainted-1.c          |  88 +++++
>>>   .../gcc.dg/analyzer/attr-tainted-misuses.c    |   6 +
>>>   .../gcc.dg/analyzer/taint-CVE-2011-2210-1.c   |  93 +++++
>>>   .../gcc.dg/analyzer/taint-CVE-2020-13143-1.c  |  38 +++
>>>   .../gcc.dg/analyzer/taint-CVE-2020-13143-2.c  |  32 ++
>>>   .../gcc.dg/analyzer/taint-CVE-2020-13143.h    |  91 +++++
>>>   gcc/testsuite/gcc.dg/analyzer/taint-alloc-3.c |  21 ++
>>>   gcc/testsuite/gcc.dg/analyzer/taint-alloc-4.c |  31 ++
>>>   11 files changed, 772 insertions(+), 3 deletions(-)
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/attr-tainted-1.c
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/attr-tainted-
>>> misuses.c
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/taint-CVE-2011-
>>> 2210-1.c
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-
>>> 13143-1.c
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-
>>> 13143-2.c
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-
>>> 13143.h
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/taint-alloc-3.c
>>>   create mode 100644 gcc/testsuite/gcc.dg/analyzer/taint-alloc-4.c
>>>
>>> diff --git a/gcc/analyzer/engine.cc b/gcc/analyzer/engine.cc
>>> index 096e219392d..5fab41daf93 100644
>>> --- a/gcc/analyzer/engine.cc
>>> +++ b/gcc/analyzer/engine.cc
>>> @@ -68,6 +68,9 @@ along with GCC; see the file COPYING3.  If not see
>>>   #include "plugin.h"
>>>   #include "target.h"
>>>   #include <memory>
>>> +#include "stringpool.h"
>>> +#include "attribs.h"
>>> +#include "tree-dfa.h"
>>>   
>>>   /* For an overview, see gcc/doc/analyzer.texi.  */
>>>   
>>> @@ -2276,6 +2279,116 @@ exploded_graph::~exploded_graph ()
>>>       delete (*iter).second;
>>>   }
>>>   
>>> +/* Subroutine for use when implementing __attribute__((tainted))
>>> +   on functions and on function pointer fields in structs.
>>> +
>>> +   Called on STATE representing a call to FNDECL.
>>> +   Mark all params of FNDECL in STATE as "tainted".  Mark the value
>>> of all
>>> +   regions pointed to by params of FNDECL as "tainted".
>>> +
>>> +   Return true if successful; return false if the "taint" state
>>> machine
>>> +   was not found.  */
>>> +
>>> +static bool
>>> +mark_params_as_tainted (program_state *state, tree fndecl,
>>> +                       const extrinsic_state &ext_state)
>>> +{
>>> +  unsigned taint_sm_idx;
>>> +  if (!ext_state.get_sm_idx_by_name ("taint", &taint_sm_idx))
>>> +    return false;
>>> +  sm_state_map *smap = state->m_checker_states[taint_sm_idx];
>>> +
>>> +  const state_machine &sm = ext_state.get_sm (taint_sm_idx);
>>> +  state_machine::state_t tainted = sm.get_state_by_name ("tainted");
>>> +
>>> +  region_model_manager *mgr = ext_state.get_model_manager ();
>>> +
>>> +  function *fun = DECL_STRUCT_FUNCTION (fndecl);
>>> +  gcc_assert (fun);
>>> +
>>> +  for (tree iter_parm = DECL_ARGUMENTS (fndecl); iter_parm;
>>> +       iter_parm = DECL_CHAIN (iter_parm))
>>> +    {
>>> +      tree param = iter_parm;
>>> +      if (tree parm_default_ssa = ssa_default_def (fun, iter_parm))
>>> +       param = parm_default_ssa;
>>> +      const region *param_reg = state->m_region_model->get_lvalue
>>> (param, NULL);
>>> +      const svalue *init_sval = mgr->get_or_create_initial_value
>>> (param_reg);
>>> +      smap->set_state (state->m_region_model, init_sval,
>>> +                      tainted, NULL /*origin_new_sval*/, ext_state);
>>> +      if (POINTER_TYPE_P (TREE_TYPE (param)))
>>> +       {
>>> +         const region *pointee_reg = mgr->get_symbolic_region
>>> (init_sval);
>>> +         /* Mark "*param" as tainted.  */
>>> +         const svalue *init_pointee_sval
>>> +           = mgr->get_or_create_initial_value (pointee_reg);
>>> +         smap->set_state (state->m_region_model, init_pointee_sval,
>>> +                          tainted, NULL /*origin_new_sval*/,
>>> ext_state);
>>> +       }
>>> +    }
>>> +
>>> +  return true;
>>> +}
>>> +
>>> +/* Custom event for use by tainted_function_info when a function
>>> +   has been marked with __attribute__((tainted)).  */
>>> +
>>> +class tainted_function_custom_event : public custom_event
>>> +{
>>> +public:
>>> +  tainted_function_custom_event (location_t loc, tree fndecl, int
>>> depth)
>>> +  : custom_event (loc, fndecl, depth),
>>> +    m_fndecl (fndecl)
>>> +  {
>>> +  }
>>> +
>>> +  label_text get_desc (bool can_colorize) const FINAL OVERRIDE
>>> +  {
>>> +    return make_label_text
>>> +      (can_colorize,
>>> +       "function %qE marked with %<__attribute__((tainted))%>",
>>> +       m_fndecl);
>>> +  }
>>> +
>>> +private:
>>> +  tree m_fndecl;
>>> +};
>>> +
>>> +/* Custom exploded_edge info for top-level calls to a function
>>> +   marked with __attribute__((tainted)).  */
>>> +
>>> +class tainted_function_info : public custom_edge_info
>>> +{
>>> +public:
>>> +  tainted_function_info (tree fndecl)
>>> +  : m_fndecl (fndecl)
>>> +  {}
>>> +
>>> +  void print (pretty_printer *pp) const FINAL OVERRIDE
>>> +  {
>>> +    pp_string (pp, "call to tainted function");
>>> +  };
>>> +
>>> +  bool update_model (region_model *,
>>> +                    const exploded_edge *,
>>> +                    region_model_context *) const FINAL OVERRIDE
>>> +  {
>>> +    /* No-op.  */
>>> +    return true;
>>> +  }
>>> +
>>> +  void add_events_to_path (checker_path *emission_path,
>>> +                          const exploded_edge &) const FINAL
>>> OVERRIDE
>>> +  {
>>> +    emission_path->add_event
>>> +      (new tainted_function_custom_event
>>> +       (DECL_SOURCE_LOCATION (m_fndecl), m_fndecl, 0));
>>> +  }
>>> +
>>> +private:
>>> +  tree m_fndecl;
>>> +};
>>> +
>>>   /* Ensure that there is an exploded_node representing an external
>>> call to
>>>      FUN, adding it to the worklist if creating it.
>>>   
>>> @@ -2302,14 +2415,25 @@ exploded_graph::add_function_entry (function
>>> *fun)
>>>     program_state state (m_ext_state);
>>>     state.push_frame (m_ext_state, fun);
>>>   
>>> +  custom_edge_info *edge_info = NULL;
>>> +
>>> +  if (lookup_attribute ("tainted", DECL_ATTRIBUTES (fun->decl)))
>>> +    {
>>> +      if (mark_params_as_tainted (&state, fun->decl, m_ext_state))
>>> +       edge_info = new tainted_function_info (fun->decl);
>>> +    }
>>> +
>>>     if (!state.m_valid)
>>>       return NULL;
>>>   
>>>     exploded_node *enode = get_or_create_node (point, state, NULL);
>>>     if (!enode)
>>> -    return NULL;
>>> +    {
>>> +      delete edge_info;
>>> +      return NULL;
>>> +    }
>>>   
>>> -  add_edge (m_origin, enode, NULL);
>>> +  add_edge (m_origin, enode, NULL, edge_info);
>>>   
>>>     m_functions_with_enodes.add (fun);
>>>   
>>> @@ -2623,6 +2747,184 @@ toplevel_function_p (function *fun, logger
>>> *logger)
>>>     return true;
>>>   }
>>>   
>>> +/* Custom event for use by tainted_call_info when a callback field
>>> has been
>>> +   marked with __attribute__((tainted)), for labelling the field.
>>> */
>>> +
>>> +class tainted_field_custom_event : public custom_event
>>> +{
>>> +public:
>>> +  tainted_field_custom_event (tree field)
>>> +  : custom_event (DECL_SOURCE_LOCATION (field), NULL_TREE, 0),
>>> +    m_field (field)
>>> +  {
>>> +  }
>>> +
>>> +  label_text get_desc (bool can_colorize) const FINAL OVERRIDE
>>> +  {
>>> +    return make_label_text (can_colorize,
>>> +                           "field %qE of %qT"
>>> +                           " is marked with
>>> %<__attribute__((tainted))%>",
>>> +                           m_field, DECL_CONTEXT (m_field));
>>> +  }
>>> +
>>> +private:
>>> +  tree m_field;
>>> +};
>>> +
>>> +/* Custom event for use by tainted_call_info when a callback field
>>> has been
>>> +   marked with __attribute__((tainted)), for labelling the function
>>> used
>>> +   in that callback.  */
>>> +
>>> +class tainted_callback_custom_event : public custom_event
>>> +{
>>> +public:
>>> +  tainted_callback_custom_event (location_t loc, tree fndecl, int
>>> depth,
>>> +                                tree field)
>>> +  : custom_event (loc, fndecl, depth),
>>> +    m_field (field)
>>> +  {
>>> +  }
>>> +
>>> +  label_text get_desc (bool can_colorize) const FINAL OVERRIDE
>>> +  {
>>> +    return make_label_text (can_colorize,
>>> +                           "function %qE used as initializer for
>>> field %qE"
>>> +                           " marked with
>>> %<__attribute__((tainted))%>",
>>> +                           m_fndecl, m_field);
>>> +  }
>>> +
>>> +private:
>>> +  tree m_field;
>>> +};
>>> +
>>> +/* Custom edge info for use when adding a function used by a
>>> callback field
>>> +   marked with '__attribute__((tainted))'.   */
>>> +
>>> +class tainted_call_info : public custom_edge_info
>>> +{
>>> +public:
>>> +  tainted_call_info (tree field, tree fndecl, location_t loc)
>>> +  : m_field (field), m_fndecl (fndecl), m_loc (loc)
>>> +  {}
>>> +
>>> +  void print (pretty_printer *pp) const FINAL OVERRIDE
>>> +  {
>>> +    pp_string (pp, "call to tainted field");
>>> +  };
>>> +
>>> +  bool update_model (region_model *,
>>> +                    const exploded_edge *,
>>> +                    region_model_context *) const FINAL OVERRIDE
>>> +  {
>>> +    /* No-op.  */
>>> +    return true;
>>> +  }
>>> +
>>> +  void add_events_to_path (checker_path *emission_path,
>>> +                          const exploded_edge &) const FINAL
>>> OVERRIDE
>>> +  {
>>> +    /* Show the field in the struct declaration
>>> +       e.g. "(1) field 'store' is marked with
>>> '__attribute__((tainted))'"  */
>>> +    emission_path->add_event
>>> +      (new tainted_field_custom_event (m_field));
>>> +
>>> +    /* Show the callback in the initializer
>>> +       e.g.
>>> +       "(2) function 'gadget_dev_desc_UDC_store' used as initializer
>>> +       for field 'store' marked with '__attribute__((tainted))'".
>>> */
>>> +    emission_path->add_event
>>> +      (new tainted_callback_custom_event (m_loc, m_fndecl, 0,
>>> m_field));
>>> +  }
>>> +
>>> +private:
>>> +  tree m_field;
>>> +  tree m_fndecl;
>>> +  location_t m_loc;
>>> +};
>>> +
>>> +/* Given an initializer at LOC for FIELD marked with
>>> '__attribute__((tainted))'
>>> +   initialized with FNDECL, add an entrypoint to FNDECL to EG (and
>>> to its
>>> +   worklist) where the params to FNDECL are marked as tainted.  */
>>> +
>>> +static void
>>> +add_tainted_callback (exploded_graph *eg, tree field, tree fndecl,
>>> +                     location_t loc)
>>> +{
>>> +  logger *logger = eg->get_logger ();
>>> +
>>> +  LOG_SCOPE (logger);
>>> +
>>> +  if (!gimple_has_body_p (fndecl))
>>> +    return;
>>> +
>>> +  const extrinsic_state &ext_state = eg->get_ext_state ();
>>> +
>>> +  function *fun = DECL_STRUCT_FUNCTION (fndecl);
>>> +  gcc_assert (fun);
>>> +
>>> +  program_point point
>>> +    = program_point::from_function_entry (eg->get_supergraph (),
>>> fun);
>>> +  program_state state (ext_state);
>>> +  state.push_frame (ext_state, fun);
>>> +
>>> +  if (!mark_params_as_tainted (&state, fndecl, ext_state))
>>> +    return;
>>> +
>>> +  if (!state.m_valid)
>>> +    return;
>>> +
>>> +  exploded_node *enode = eg->get_or_create_node (point, state,
>>> NULL);
>>> +  if (logger)
>>> +    {
>>> +      if (enode)
>>> +       logger->log ("created EN %i for tainted %qE entrypoint",
>>> +                    enode->m_index, fndecl);
>>> +      else
>>> +       {
>>> +         logger->log ("did not create enode for tainted %qE
>>> entrypoint",
>>> +                      fndecl);
>>> +         return;
>>> +       }
>>> +    }
>>> +
>>> +  tainted_call_info *info = new tainted_call_info (field, fndecl,
>>> loc);
>>> +  eg->add_edge (eg->get_origin (), enode, NULL, info);
>>> +}
>>> +
>>> +/* Callback for walk_tree for finding callbacks within initializers;
>>> +   ensure that any callback initializer where the corresponding
>>> field is
>>> +   marked with '__attribute__((tainted))' is treated as an
>>> entrypoint to the
>>> +   analysis, special-casing that the inputs to the callback are
>>> +   untrustworthy.  */
>>> +
>>> +static tree
>>> +add_any_callbacks (tree *tp, int *, void *data)
>>> +{
>>> +  exploded_graph *eg = (exploded_graph *)data;
>>> +  if (TREE_CODE (*tp) == CONSTRUCTOR)
>>> +    {
>>> +      /* Find fields with the "tainted" attribute.
>>> +        walk_tree only walks the values, not the index values;
>>> +        look at the index values.  */
>>> +      unsigned HOST_WIDE_INT idx;
>>> +      constructor_elt *ce;
>>> +
>>> +      for (idx = 0; vec_safe_iterate (CONSTRUCTOR_ELTS (*tp), idx,
>>> &ce);
>>> +          idx++)
>>> +       if (ce->index && TREE_CODE (ce->index) == FIELD_DECL)
>>> +         if (lookup_attribute ("tainted", DECL_ATTRIBUTES (ce-
>>>> index)))
>>> +           {
>>> +             tree value = ce->value;
>>> +             if (TREE_CODE (value) == ADDR_EXPR
>>> +                 && TREE_CODE (TREE_OPERAND (value, 0)) ==
>>> FUNCTION_DECL)
>>> +               add_tainted_callback (eg, ce->index, TREE_OPERAND
>>> (value, 0),
>>> +                                     EXPR_LOCATION (value));
>>> +           }
>>> +    }
>>> +
>>> +  return NULL_TREE;
>>> +}
>>> +
>>>   /* Add initial nodes to EG, with entrypoints for externally-callable
>>>      functions.  */
>>>   
>>> @@ -2648,6 +2950,17 @@ exploded_graph::build_initial_worklist ()
>>>            logger->log ("did not create enode for %qE entrypoint",
>>> fun->decl);
>>>         }
>>>     }
>>> +
>>> +  /* Find callbacks that are reachable from global initializers.  */
>>> +  varpool_node *vpnode;
>>> +  FOR_EACH_VARIABLE (vpnode)
>>> +    {
>>> +      tree decl = vpnode->decl;
>>> +      tree init = DECL_INITIAL (decl);
>>> +      if (!init)
>>> +       continue;
>>> +      walk_tree (&init, add_any_callbacks, this, NULL);
>>> +    }
>>>   }
>>>   
>>>   /* The main loop of the analysis.
>>> diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
>>> index 9e03156de5e..835ba6e0e8c 100644
>>> --- a/gcc/c-family/c-attribs.c
>>> +++ b/gcc/c-family/c-attribs.c
>>> @@ -117,6 +117,7 @@ static tree
>>> handle_no_profile_instrument_function_attribute (tree *, tree,
>>>                                                               tree,
>>> int, bool *);
>>>   static tree handle_malloc_attribute (tree *, tree, tree, int, bool
>>> *);
>>>   static tree handle_dealloc_attribute (tree *, tree, tree, int, bool
>>> *);
>>> +static tree handle_tainted_attribute (tree *, tree, tree, int, bool
>>> *);
>>>   static tree handle_returns_twice_attribute (tree *, tree, tree, int,
>>> bool *);
>>>   static tree handle_no_limit_stack_attribute (tree *, tree, tree,
>>> int,
>>>                                               bool *);
>>> @@ -569,6 +570,8 @@ const struct attribute_spec
>>> c_common_attribute_table[] =
>>>                                handle_objc_nullability_attribute, NULL
>>> },
>>>     { "*dealloc",                1, 2, true, false, false, false,
>>>                                handle_dealloc_attribute, NULL },
>>> +  { "tainted",               0, 0, true,  false, false, false,
>>> +                             handle_tainted_attribute, NULL },
>>>     { NULL,                     0, 0, false, false, false, false,
>>> NULL, NULL }
>>>   };
>>>   
>>> @@ -5857,6 +5860,39 @@ handle_objc_nullability_attribute (tree *node,
>>> tree name, tree args,
>>>     return NULL_TREE;
>>>   }
>>>   
>>> +/* Handle a "tainted" attribute; arguments as in
>>> +   struct attribute_spec.handler.  */
>>> +
>>> +static tree
>>> +handle_tainted_attribute (tree *node, tree name, tree, int,
>>> +                         bool *no_add_attrs)
>>> +{
>>> +  if (TREE_CODE (*node) != FUNCTION_DECL
>>> +      && TREE_CODE (*node) != FIELD_DECL)
>>> +    {
>>> +      warning (OPT_Wattributes, "%qE attribute ignored; valid only "
>>> +              "for functions and function pointer fields",
>>> +              name);
>>> +      *no_add_attrs = true;
>>> +      return NULL_TREE;
>>> +    }
>>> +
>>> +  if (TREE_CODE (*node) == FIELD_DECL
>>> +      && !(TREE_CODE (TREE_TYPE (*node)) == POINTER_TYPE
>>> +          && TREE_CODE (TREE_TYPE (TREE_TYPE (*node))) ==
>>> FUNCTION_TYPE))
>>> +    {
>>> +      warning (OPT_Wattributes, "%qE attribute ignored;"
>>> +              " field must be a function pointer",
>>> +              name);
>>> +      *no_add_attrs = true;
>>> +      return NULL_TREE;
>>> +    }
>>> +
>>> +  *no_add_attrs = false; /* OK */
>>> +
>>> +  return NULL_TREE;
>>> +}
>>> +
>>>   /* Attempt to partially validate a single attribute ATTR as if
>>>      it were to be applied to an entity OPER.  */
>>>   
>>> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
>>> index 5a6ef464779..826bbd48e7e 100644
>>> --- a/gcc/doc/extend.texi
>>> +++ b/gcc/doc/extend.texi
>>> @@ -2465,7 +2465,8 @@ variable declarations (@pxref{Variable
>>> Attributes}),
>>>   labels (@pxref{Label Attributes}),
>>>   enumerators (@pxref{Enumerator Attributes}),
>>>   statements (@pxref{Statement Attributes}),
>>> -and types (@pxref{Type Attributes}).
>>> +types (@pxref{Type Attributes}),
>>> +and on field declarations (for @code{tainted}).
>>>   
>>>   There is some overlap between the purposes of attributes and pragmas
>>>   (@pxref{Pragmas,,Pragmas Accepted by GCC}).  It has been
>>> @@ -3977,6 +3978,25 @@ addition to creating a symbol version (as if
>>>   @code{"@var{name2}@@@var{nodename}"} was used) the version will be
>>> also used
>>>   to resolve @var{name2} by the linker.
>>>   
>>> +@item tainted
>>> +@cindex @code{tainted} function attribute
>>> +The @code{tainted} attribute is used to specify that a function is
>>> called
>>> +in a way that requires sanitization of its arguments, such as a
>>> system
>>> +call in an operating system kernel.  Such a function can be
>>> considered part
>>> +of the ``attack surface'' of the program.  The attribute can be used
>>> both
>>> +on function declarations, and on field declarations containing
>>> function
>>> +pointers.  In the latter case, any function used as an initializer
>>> of
>>> +such a callback field will be treated as tainted.
>>> +
>>> +The analyzer will pay particular attention to such functions when
>>> both
>>> +@option{-fanalyzer} and @option{-fanalyzer-checker=taint} are
>>> supplied,
>>> +potentially issuing warnings guarded by
>>> +@option{-Wanalyzer-exposure-through-uninit-copy},
>>> +@option{-Wanalyzer-tainted-allocation-size},
>>> +@option{-Wanalyzer-tainted-array-index},
>>> +@option{Wanalyzer-tainted-offset},
>>> +and @option{Wanalyzer-tainted-size}.
>>> +
>>>   @item target_clones (@var{options})
>>>   @cindex @code{target_clones} function attribute
>>>   The @code{target_clones} attribute is used to specify that a
>>> function
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/attr-tainted-1.c
>>> b/gcc/testsuite/gcc.dg/analyzer/attr-tainted-1.c
>>> new file mode 100644
>>> index 00000000000..cc4d5900372
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/attr-tainted-1.c
>>> @@ -0,0 +1,88 @@
>>> +// TODO: remove need for this option
>>> +/* { dg-additional-options "-fanalyzer-checker=taint" } */
>>> +
>>> +#include "analyzer-decls.h"
>>> +
>>> +struct arg_buf
>>> +{
>>> +  int i;
>>> +  int j;
>>> +};
>>> +
>>> +/* Example of marking a function as tainted.  */
>>> +
>>> +void __attribute__((tainted))
>>> +test_1 (int i, void *p, char *q)
>>> +{
>>> +  /* There should be a single enode,
>>> +     for the "tainted" entry to the function.  */
>>> +  __analyzer_dump_exploded_nodes (0); /* { dg-warning "1 processed
>>> enode" } */
>>> +
>>> +  __analyzer_dump_state ("taint", i); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +  __analyzer_dump_state ("taint", p); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +  __analyzer_dump_state ("taint", q); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +  __analyzer_dump_state ("taint", *q); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +
>>> +  struct arg_buf *args = p;
>>> +  __analyzer_dump_state ("taint", args->i); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +  __analyzer_dump_state ("taint", args->j); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +}
>>> +
>>> +/* Example of marking a callback field as tainted.  */
>>> +
>>> +struct s2
>>> +{
>>> +  void (*cb) (int, void *, char *)
>>> +    __attribute__((tainted));
>>> +};
>>> +
>>> +/* Function not marked as tainted.  */
>>> +
>>> +void
>>> +test_2a (int i, void *p, char *q)
>>> +{
>>> +  /* There should be a single enode,
>>> +     for the normal entry to the function.  */
>>> +  __analyzer_dump_exploded_nodes (0); /* { dg-warning "1 processed
>>> enode" } */
>>> +
>>> +  __analyzer_dump_state ("taint", i); /* { dg-warning "state:
>>> 'start'" } */
>>> +  __analyzer_dump_state ("taint", p); /* { dg-warning "state:
>>> 'start'" } */
>>> +  __analyzer_dump_state ("taint", q); /* { dg-warning "state:
>>> 'start'" } */
>>> +
>>> +  struct arg_buf *args = p;
>>> +  __analyzer_dump_state ("taint", args->i); /* { dg-warning "state:
>>> 'start'" } */
>>> +  __analyzer_dump_state ("taint", args->j); /* { dg-warning "state:
>>> 'start'" } */
>>> +}
>>> +
>>> +/* Function referenced via t2b.cb, marked as "tainted".  */
>>> +
>>> +void
>>> +test_2b (int i, void *p, char *q)
>>> +{
>>> +  /* There should be two enodes
>>> +     for the direct call, and the "tainted" entry to the function.
>>> */
>>> +  __analyzer_dump_exploded_nodes (0); /* { dg-warning "2 processed
>>> enodes" } */
>>> +}
>>> +
>>> +/* Callback used via t2c.cb, marked as "tainted".  */
>>> +void
>>> +__analyzer_test_2c (int i, void *p, char *q)
>>> +{
>>> +  /* There should be a single enode,
>>> +     for the "tainted" entry to the function.  */
>>> +  __analyzer_dump_exploded_nodes (0); /* { dg-warning "1 processed
>>> enode" } */
>>> +
>>> +  __analyzer_dump_state ("taint", i); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +  __analyzer_dump_state ("taint", p); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +  __analyzer_dump_state ("taint", q); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +}
>>> +
>>> +struct s2 t2b =
>>> +{
>>> +  .cb = test_2b
>>> +};
>>> +
>>> +struct s2 t2c =
>>> +{
>>> +  .cb = __analyzer_test_2c
>>> +};
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/attr-tainted-misuses.c
>>> b/gcc/testsuite/gcc.dg/analyzer/attr-tainted-misuses.c
>>> new file mode 100644
>>> index 00000000000..6f4cbc82efb
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/attr-tainted-misuses.c
>>> @@ -0,0 +1,6 @@
>>> +int not_a_fn __attribute__ ((tainted)); /* { dg-warning "'tainted'
>>> attribute ignored; valid only for functions and function pointer
>>> fields" } */
>>> +
>>> +struct s
>>> +{
>>> +  int f __attribute__ ((tainted)); /* { dg-warning "'tainted'
>>> attribute ignored; field must be a function pointer" } */
>>> +};
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2011-2210-1.c
>>> b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2011-2210-1.c
>>> new file mode 100644
>>> index 00000000000..fe6c7ebbb1f
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2011-2210-1.c
>>> @@ -0,0 +1,93 @@
>>> +/* "The osf_getsysinfo function in arch/alpha/kernel/osf_sys.c in
>>> the
>>> +   Linux kernel before 2.6.39.4 on the Alpha platform does not
>>> properly
>>> +   restrict the data size for GSI_GET_HWRPB operations, which allows
>>> +   local users to obtain sensitive information from kernel memory
>>> via
>>> +   a crafted call."
>>> +
>>> +   Fixed in 3d0475119d8722798db5e88f26493f6547a4bb5b on linux-
>>> 2.6.39.y
>>> +   in linux-stable.  */
>>> +
>>> +// TODO: remove need for this option:
>>> +/* { dg-additional-options "-fanalyzer-checker=taint" } */
>>> +
>>> +#include "analyzer-decls.h"
>>> +#include "test-uaccess.h"
>>> +
>>> +/* Adapted from include/linux/linkage.h.  */
>>> +
>>> +#define asmlinkage
>>> +
>>> +/* Adapted from include/linux/syscalls.h.  */
>>> +
>>> +#define __SC_DECL1(t1, a1)     t1 a1
>>> +#define __SC_DECL2(t2, a2, ...) t2 a2, __SC_DECL1(__VA_ARGS__)
>>> +#define __SC_DECL3(t3, a3, ...) t3 a3, __SC_DECL2(__VA_ARGS__)
>>> +#define __SC_DECL4(t4, a4, ...) t4 a4, __SC_DECL3(__VA_ARGS__)
>>> +#define __SC_DECL5(t5, a5, ...) t5 a5, __SC_DECL4(__VA_ARGS__)
>>> +#define __SC_DECL6(t6, a6, ...) t6 a6, __SC_DECL5(__VA_ARGS__)
>>> +
>>> +#define SYSCALL_DEFINEx(x, sname, ...)                         \
>>> +       __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
>>> +
>>> +#define SYSCALL_DEFINE(name) asmlinkage long sys_##name
>>> +#define __SYSCALL_DEFINEx(x, name,
>>> ...)                                        \
>>> +       asmlinkage __attribute__((tainted)) \
>>> +       long sys##name(__SC_DECL##x(__VA_ARGS__))
>>> +
>>> +#define SYSCALL_DEFINE5(name, ...) SYSCALL_DEFINEx(5, _##name,
>>> __VA_ARGS__)
>>> +
>>> +/* Adapted from arch/alpha/include/asm/hwrpb.h.  */
>>> +
>>> +struct hwrpb_struct {
>>> +       unsigned long phys_addr;        /* check: physical address of
>>> the hwrpb */
>>> +       unsigned long id;               /* check: "HWRPB\0\0\0" */
>>> +       unsigned long revision;
>>> +       unsigned long size;             /* size of hwrpb */
>>> +       /* [...snip...] */
>>> +};
>>> +
>>> +extern struct hwrpb_struct *hwrpb;
>>> +
>>> +/* Adapted from arch/alpha/kernel/osf_sys.c.  */
>>> +
>>> +SYSCALL_DEFINE5(osf_getsysinfo, unsigned long, op, void __user *,
>>> buffer,
>>> +               unsigned long, nbytes, int __user *, start, void
>>> __user *, arg)
>>> +{
>>> +       /* [...snip...] */
>>> +
>>> +       __analyzer_dump_state ("taint", nbytes);  /* { dg-warning
>>> "tainted" } */
>>> +
>>> +       /* TODO: should have an event explaining why "nbytes" is
>>> treated as
>>> +          attacker-controlled.  */
>>> +
>>> +       /* case GSI_GET_HWRPB: */
>>> +               if (nbytes < sizeof(*hwrpb))
>>> +                       return -1;
>>> +
>>> +               __analyzer_dump_state ("taint", nbytes);  /* { dg-
>>> warning "has_lb" } */
>>> +
>>> +               if (copy_to_user(buffer, hwrpb, nbytes) != 0) /* {
>>> dg-warning "use of attacker-controlled value 'nbytes' as size without
>>> upper-bounds checking" } */
>>> +                       return -2;
>>> +
>>> +               return 1;
>>> +
>>> +       /* [...snip...] */
>>> +}
>>> +
>>> +/* With the fix for the sense of the size comparison.  */
>>> +
>>> +SYSCALL_DEFINE5(osf_getsysinfo_fixed, unsigned long, op, void __user
>>> *, buffer,
>>> +               unsigned long, nbytes, int __user *, start, void
>>> __user *, arg)
>>> +{
>>> +       /* [...snip...] */
>>> +
>>> +       /* case GSI_GET_HWRPB: */
>>> +               if (nbytes > sizeof(*hwrpb))
>>> +                       return -1;
>>> +               if (copy_to_user(buffer, hwrpb, nbytes) != 0) /* {
>>> dg-bogus "attacker-controlled" } */
>>> +                       return -2;
>>> +
>>> +               return 1;
>>> +
>>> +       /* [...snip...] */
>>> +}
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143-1.c
>>> b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143-1.c
>>> new file mode 100644
>>> index 00000000000..0b9a94a8d6c
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143-1.c
>>> @@ -0,0 +1,38 @@
>>> +/* See notes in this header.  */
>>> +#include "taint-CVE-2020-13143.h"
>>> +
>>> +// TODO: remove need for this option
>>> +/* { dg-additional-options "-fanalyzer-checker=taint" } */
>>> +
>>> +struct configfs_attribute {
>>> +       /* [...snip...] */
>>> +       ssize_t (*store)(struct config_item *, const char *, size_t)
>>> /* { dg-message "\\(1\\) field 'store' of 'struct configfs_attribute'
>>> is marked with '__attribute__\\(\\(tainted\\)\\)'" } */
>>> +               __attribute__((tainted)); /* (this is added).  */
>>> +};
>>> +static inline struct gadget_info *to_gadget_info(struct config_item
>>> *item)
>>> +{
>>> +        return container_of(to_config_group(item), struct
>>> gadget_info, group);
>>> +}
>>> +
>>> +static ssize_t gadget_dev_desc_UDC_store(struct config_item *item,
>>> +               const char *page, size_t len)
>>> +{
>>> +       struct gadget_info *gi = to_gadget_info(item);
>>> +       char *name;
>>> +       int ret;
>>> +
>>> +#if 0
>>> +       /* FIXME: this is the fix.  */
>>> +       if (strlen(page) < len)
>>> +               return -EOVERFLOW;
>>> +#endif
>>> +
>>> +       name = kstrdup(page, GFP_KERNEL);
>>> +       if (!name)
>>> +               return -ENOMEM;
>>> +       if (name[len - 1] == '\n') /* { dg-warning "use of attacker-
>>> controlled value 'len \[^\n\r\]+' as offset without upper-bounds
>>> checking" } */
>>> +               name[len - 1] = '\0'; /* { dg-warning "use of
>>> attacker-controlled value 'len \[^\n\r\]+' as offset without upper-
>>> bounds checking" } */
>>> +       /* [...snip...] */                              \
>>> +}
>>> +
>>> +CONFIGFS_ATTR(gadget_dev_desc_, UDC); /* { dg-message "\\(2\\)
>>> function 'gadget_dev_desc_UDC_store' used as initializer for field
>>> 'store' marked with '__attribute__\\(\\(tainted\\)\\)'" } */
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143-2.c
>>> b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143-2.c
>>> new file mode 100644
>>> index 00000000000..e05da9276c1
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143-2.c
>>> @@ -0,0 +1,32 @@
>>> +/* See notes in this header.  */
>>> +#include "taint-CVE-2020-13143.h"
>>> +
>>> +// TODO: remove need for this option
>>> +/* { dg-additional-options "-fanalyzer-checker=taint" } */
>>> +
>>> +struct configfs_attribute {
>>> +       /* [...snip...] */
>>> +       ssize_t (*store)(struct config_item *, const char *, size_t)
>>> /* { dg-message "\\(1\\) field 'store' of 'struct configfs_attribute'
>>> is marked with '__attribute__\\(\\(tainted\\)\\)'" } */
>>> +               __attribute__((tainted)); /* (this is added).  */
>>> +};
>>> +
>>> +/* Highly simplified version.  */
>>> +
>>> +static ssize_t gadget_dev_desc_UDC_store(struct config_item *item,
>>> +               const char *page, size_t len)
>>> +{
>>> +       /* TODO: ought to have state_change_event talking about where
>>> the tainted value comes from.  */
>>> +
>>> +       char *name;
>>> +       /* [...snip...] */
>>> +
>>> +       name = kstrdup(page, GFP_KERNEL);
>>> +       if (!name)
>>> +               return -ENOMEM;
>>> +       if (name[len - 1] == '\n') /* { dg-warning "use of attacker-
>>> controlled value 'len \[^\n\r\]+' as offset without upper-bounds
>>> checking" } */
>>> +               name[len - 1] = '\0';  /* { dg-warning "use of
>>> attacker-controlled value 'len \[^\n\r\]+' as offset without upper-
>>> bounds checking" } */
>>> +       /* [...snip...] */
>>> +       return 0;
>>> +}
>>> +
>>> +CONFIGFS_ATTR(gadget_dev_desc_, UDC); /* { dg-message "\\(2\\)
>>> function 'gadget_dev_desc_UDC_store' used as initializer for field
>>> 'store' marked with '__attribute__\\(\\(tainted\\)\\)'" } */
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143.h
>>> b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143.h
>>> new file mode 100644
>>> index 00000000000..0ba023539af
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/taint-CVE-2020-13143.h
>>> @@ -0,0 +1,91 @@
>>> +/* Shared header for the various taint-CVE-2020-13143.h tests.
>>> +
>>> +   "gadget_dev_desc_UDC_store in drivers/usb/gadget/configfs.c in
>>> the
>>> +   Linux kernel 3.16 through 5.6.13 relies on kstrdup without
>>> considering
>>> +   the possibility of an internal '\0' value, which allows attackers
>>> to
>>> +   trigger an out-of-bounds read, aka CID-15753588bcd4."
>>> +
>>> +   Fixed by 15753588bcd4bbffae1cca33c8ced5722477fe1f on linux-5.7.y
>>> +   in linux-stable.  */
>>> +
>>> +// TODO: remove need for this option
>>> +/* { dg-additional-options "-fanalyzer-checker=taint" } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +/* Adapted from include/uapi/asm-generic/posix_types.h  */
>>> +
>>> +typedef unsigned int     __kernel_size_t;
>>> +typedef int              __kernel_ssize_t;
>>> +
>>> +/* Adapted from include/linux/types.h  */
>>> +
>>> +//typedef __kernel_size_t              size_t;
>>> +typedef __kernel_ssize_t       ssize_t;
>>> +
>>> +/* Adapted from include/linux/kernel.h  */
>>> +
>>> +#define container_of(ptr, type, member)
>>> ({                             \
>>> +       void *__mptr = (void
>>> *)(ptr);                                   \
>>> +       /* [...snip...]
>>> */                                              \
>>> +       ((type *)(__mptr - offsetof(type, member))); })
>>> +
>>> +/* Adapted from include/linux/configfs.h  */
>>> +
>>> +struct config_item {
>>> +       /* [...snip...] */
>>> +};
>>> +
>>> +struct config_group {
>>> +       struct config_item              cg_item;
>>> +       /* [...snip...] */
>>> +};
>>> +
>>> +static inline struct config_group *to_config_group(struct
>>> config_item *item)
>>> +{
>>> +       return item ? container_of(item,struct config_group,cg_item)
>>> : NULL;
>>> +}
>>> +
>>> +#define CONFIGFS_ATTR(_pfx, _name)                             \
>>> +static struct configfs_attribute _pfx##attr_##_name = {        \
>>> +       /* [...snip...] */                              \
>>> +       .store          = _pfx##_name##_store,          \
>>> +}
>>> +
>>> +/* Adapted from include/linux/compiler.h  */
>>> +
>>> +#define __force
>>> +
>>> +/* Adapted from include/asm-generic/errno-base.h  */
>>> +
>>> +#define        ENOMEM          12      /* Out of memory */
>>> +
>>> +/* Adapted from include/linux/types.h  */
>>> +
>>> +#define __bitwise__
>>> +typedef unsigned __bitwise__ gfp_t;
>>> +
>>> +/* Adapted from include/linux/gfp.h  */
>>> +
>>> +#define ___GFP_WAIT            0x10u
>>> +#define ___GFP_IO              0x40u
>>> +#define ___GFP_FS              0x80u
>>> +#define __GFP_WAIT     ((__force gfp_t)___GFP_WAIT)
>>> +#define __GFP_IO       ((__force gfp_t)___GFP_IO)
>>> +#define __GFP_FS       ((__force gfp_t)___GFP_FS)
>>> +#define GFP_KERNEL  (__GFP_WAIT | __GFP_IO | __GFP_FS)
>>> +
>>> +/* Adapted from include/linux/compiler_attributes.h  */
>>> +
>>> +#define __malloc                        __attribute__((__malloc__))
>>> +
>>> +/* Adapted from include/linux/string.h  */
>>> +
>>> +extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
>>> +
>>> +/* Adapted from drivers/usb/gadget/configfs.c  */
>>> +
>>> +struct gadget_info {
>>> +       struct config_group group;
>>> +       /* [...snip...] */                              \
>>> +};
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/taint-alloc-3.c
>>> b/gcc/testsuite/gcc.dg/analyzer/taint-alloc-3.c
>>> new file mode 100644
>>> index 00000000000..4c567b2ffdf
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/taint-alloc-3.c
>>> @@ -0,0 +1,21 @@
>>> +// TODO: remove need for this option:
>>> +/* { dg-additional-options "-fanalyzer-checker=taint" } */
>>> +
>>> +#include "analyzer-decls.h"
>>> +#include <stdio.h>
>>> +#include <stdlib.h>
>>> +#include <string.h>
>>> +
>>> +/* malloc with tainted size from a syscall.  */
>>> +
>>> +void *p;
>>> +
>>> +void __attribute__((tainted))
>>> +test_1 (size_t sz) /* { dg-message "\\(1\\) function 'test_1' marked
>>> with '__attribute__\\(\\(tainted\\)\\)'" } */
>>> +{
>>> +  /* TODO: should have a message saying why "sz" is tainted, e.g.
>>> +     "treating 'sz' as attacker-controlled because 'test_1' is
>>> marked with '__attribute__((tainted))'"  */
>>> +
>>> +  p = malloc (sz); /* { dg-warning "use of attacker-controlled value
>>> 'sz' as allocation size without upper-bounds checking" "warning" } */
>>> +  /* { dg-message "\\(\[0-9\]+\\) use of attacker-controlled value
>>> 'sz' as allocation size without upper-bounds checking" "final event"
>>> { target *-*-* } .-1 } */
>>> +}
>>> diff --git a/gcc/testsuite/gcc.dg/analyzer/taint-alloc-4.c
>>> b/gcc/testsuite/gcc.dg/analyzer/taint-alloc-4.c
>>> new file mode 100644
>>> index 00000000000..f52cafcd71d
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/analyzer/taint-alloc-4.c
>>> @@ -0,0 +1,31 @@
>>> +// TODO: remove need for this option:
>>> +/* { dg-additional-options "-fanalyzer-checker=taint" } */
>>> +
>>> +#include "analyzer-decls.h"
>>> +#include <stdio.h>
>>> +#include <stdlib.h>
>>> +#include <string.h>
>>> +
>>> +/* malloc with tainted size from a syscall.  */
>>> +
>>> +struct arg_buf
>>> +{
>>> +  size_t sz;
>>> +};
>>> +
>>> +void *p;
>>> +
>>> +void __attribute__((tainted))
>>> +test_1 (void *data) /* { dg-message "\\(1\\) function 'test_1'
>>> marked with '__attribute__\\(\\(tainted\\)\\)'" } */
>>> +{
>>> +  /* we should treat pointed-to-structs as tainted.  */
>>> +  __analyzer_dump_state ("taint", data); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +
>>> +  struct arg_buf *args = data;
>>> +
>>> +  __analyzer_dump_state ("taint", args); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +  __analyzer_dump_state ("taint", args->sz); /* { dg-warning "state:
>>> 'tainted'" } */
>>> +
>>> +  p = malloc (args->sz); /* { dg-warning "use of attacker-controlled
>>> value '\\*args.sz' as allocation size without upper-bounds checking"
>>> "warning" } */
>>> +  /* { dg-message "\\(\[0-9\]+\\) use of attacker-controlled value
>>> '\\*args.sz' as allocation size without upper-bounds checking" "final
>>> event" { target *-*-* } .-1 } */
>>> +}
>>
> 
>