[binutils-gdb] Aarch64: Better termination checks for sigcontext reading

[Alan Hayward <alahay01 at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=74b3c713184abb8e07f92c4e069ebafde78c0a0e

commit 74b3c713184abb8e07f92c4e069ebafde78c0a0e
Author: Alan Hayward <alan.hayward@arm.com>
Date:   Fri Oct 19 13:51:00 2018 +0100

    Aarch64: Better termination checks for sigcontext reading
    
    When reading the reserved section in the sigcontext ensure the
    address is updated on an unknown section. Also add additional
    checks to prevent reading past the end of the array.
    
    Fixes gdb.base/savedregs.exp
    
    	* aarch64-linux-tdep.c (AARCH64_SIGCONTEXT_RESERVED_SIZE): New
    	define.
    	(aarch64_linux_sigframe_init): Extra boundary checks.

Diff:
---
 gdb/ChangeLog            |  6 ++++++
 gdb/aarch64-linux-tdep.c | 17 +++++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index c203799..da613eb 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2018-10-19  Alan Hayward  <alan.hayward@arm.com>
+
+	* aarch64-linux-tdep.c (AARCH64_SIGCONTEXT_RESERVED_SIZE): New
+	define.
+	(aarch64_linux_sigframe_init): Extra boundary checks.
+
 2018-10-19  Andreas Arnez  <arnez@linux.ibm.com>
 
 	* s390-tdep.c (s390_pseudo_register_type): For v0-v15 don't yield
diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index f296207..d6dfbb6 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -137,6 +137,8 @@
 #define AARCH64_SIGCONTEXT_XO_OFFSET            8
 #define AARCH64_SIGCONTEXT_RESERVED_OFFSET      288
 
+#define AARCH64_SIGCONTEXT_RESERVED_SIZE	4096
+
 /* Unique identifiers that may be used for aarch64_ctx.magic.  */
 #define AARCH64_EXTRA_MAGIC			0x45585401
 #define AARCH64_FPSIMD_MAGIC			0x46508001
@@ -197,9 +199,11 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
   CORE_ADDR sigcontext_addr = (sp + AARCH64_RT_SIGFRAME_UCONTEXT_OFFSET
 			       + AARCH64_UCONTEXT_SIGCONTEXT_OFFSET );
   CORE_ADDR section = sigcontext_addr + AARCH64_SIGCONTEXT_RESERVED_OFFSET;
+  CORE_ADDR section_end = section + AARCH64_SIGCONTEXT_RESERVED_SIZE;
   CORE_ADDR fpsimd = 0;
   CORE_ADDR sve_regs = 0;
   uint32_t size, magic;
+  bool extra_found = false;
   int num_regs = gdbarch_num_regs (gdbarch);
 
   /* Read in the integer registers.  */
@@ -218,8 +222,9 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
 			   sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET
 			     + 32 * AARCH64_SIGCONTEXT_REG_SIZE);
 
-  /* Find the FP and SVE sections.  */
-  while ((magic = read_aarch64_ctx (section, byte_order, &size)) != 0)
+  /* Search for the FP and SVE sections, stopping at null.  */
+  while ((magic = read_aarch64_ctx (section, byte_order, &size)) != 0
+	 && size != 0)
     {
       switch (magic)
 	{
@@ -273,12 +278,20 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
 	      }
 
 	    section = extract_unsigned_integer (buf, 8, byte_order);
+	    extra_found = true;
 	    break;
 	  }
 
 	default:
+	  section += size;
 	  break;
 	}
+
+      /* Prevent searching past the end of the reserved section.  The extra
+	 section does not have a hard coded limit - we have to rely on it ending
+	 with nulls.  */
+      if (!extra_found && section > section_end)
+	break;
     }
 
   if (sve_regs != 0)