[gcc r12-6945] libiberty: Fix infinite recursion in rust demangler.

[Nick Clifton <nickc@gcc.gnu.org>]

https://gcc.gnu.org/g:f10bec5ffa487ad3033ed5f38cfd0fc7d696deab

commit r12-6945-gf10bec5ffa487ad3033ed5f38cfd0fc7d696deab
Author: Nick Clifton <nickc@redhat.com>
Date:   Mon Jan 31 14:28:42 2022 +0000

    libiberty: Fix infinite recursion in rust demangler.
    
    libiberty/
            PR demangler/98886
            PR demangler/99935
            * rust-demangle.c (struct rust_demangler): Add a recursion
            counter.
            (demangle_path): Increment/decrement the recursion counter upon
            entry and exit.  Fail if the counter exceeds a fixed limit.
            (demangle_type): Likewise.
            (rust_demangle_callback): Initialise the recursion counter,
            disabling if requested by the option flags.

Diff:
---
 libiberty/rust-demangle.c | 47 +++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 6 deletions(-)

diff --git a/libiberty/rust-demangle.c b/libiberty/rust-demangle.c
index 18c760491bd..3b24d63892a 100644
--- a/libiberty/rust-demangle.c
+++ b/libiberty/rust-demangle.c
@@ -74,6 +74,12 @@ struct rust_demangler
   /* Rust mangling version, with legacy mangling being -1. */
   int version;
 
+  /* Recursion depth.  */
+  unsigned int recursion;
+  /* Maximum number of times demangle_path may be called recursively.  */
+#define RUST_MAX_RECURSION_COUNT  1024
+#define RUST_NO_RECURSION_LIMIT   ((unsigned int) -1)
+
   uint64_t bound_lifetime_depth;
 };
 
@@ -671,6 +677,15 @@ demangle_path (struct rust_demangler *rdm, int in_value)
   if (rdm->errored)
     return;
 
+  if (rdm->recursion != RUST_NO_RECURSION_LIMIT)
+    {
+      ++ rdm->recursion;
+      if (rdm->recursion > RUST_MAX_RECURSION_COUNT)
+	/* FIXME: There ought to be a way to report
+	   that the recursion limit has been reached.  */
+	goto fail_return;
+    }
+
   switch (tag = next (rdm))
     {
     case 'C':
@@ -688,10 +703,7 @@ demangle_path (struct rust_demangler *rdm, int in_value)
     case 'N':
       ns = next (rdm);
       if (!ISLOWER (ns) && !ISUPPER (ns))
-        {
-          rdm->errored = 1;
-          return;
-        }
+	goto fail_return;
 
       demangle_path (rdm, in_value);
 
@@ -776,9 +788,15 @@ demangle_path (struct rust_demangler *rdm, int in_value)
         }
       break;
     default:
-      rdm->errored = 1;
-      return;
+      goto fail_return;
     }
+  goto pass_return;
+
+ fail_return:
+  rdm->errored = 1;
+ pass_return:
+  if (rdm->recursion != RUST_NO_RECURSION_LIMIT)
+    -- rdm->recursion;
 }
 
 static void
@@ -870,6 +888,19 @@ demangle_type (struct rust_demangler *rdm)
       return;
     }
 
+   if (rdm->recursion != RUST_NO_RECURSION_LIMIT)
+    {
+      ++ rdm->recursion;
+      if (rdm->recursion > RUST_MAX_RECURSION_COUNT)
+	/* FIXME: There ought to be a way to report
+	   that the recursion limit has been reached.  */
+	{
+	  rdm->errored = 1;
+	  -- rdm->recursion;
+	  return;
+	}
+    }
+
   switch (tag)
     {
     case 'R':
@@ -1030,6 +1061,9 @@ demangle_type (struct rust_demangler *rdm)
       rdm->next--;
       demangle_path (rdm, 0);
     }
+
+  if (rdm->recursion != RUST_NO_RECURSION_LIMIT)
+    -- rdm->recursion;
 }
 
 /* A trait in a trait object may have some "existential projections"
@@ -1320,6 +1354,7 @@ rust_demangle_callback (const char *mangled, int options,
   rdm.skipping_printing = 0;
   rdm.verbose = (options & DMGL_VERBOSE) != 0;
   rdm.version = 0;
+  rdm.recursion = (options & DMGL_NO_RECURSE_LIMIT) ? RUST_NO_RECURSION_LIMIT : 0;
   rdm.bound_lifetime_depth = 0;
 
   /* Rust symbols always start with _R (v0) or _ZN (legacy). */