[LLVMbugs] [Bug 9256] New: clang: support for kernel code model: pointer arithmetic that overflows is not impossible!

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=9256

           Summary: clang: support for kernel code model: pointer
                    arithmetic that overflows is not impossible!
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: edwintorok at gmail.com
                CC: llvmbugs at cs.uiuc.edu
        Depends on: 4068


Just a reminder that kernel/s lib/vsprintf.c still needs this patch, because
pointer arithmetic overflows, and clang's optimizer assume pointer arithmetic
never overflows.
In the kernel it is very much possible to overflow, and we must calculate the
correct value, because it is then used in an 'if' for bounds checking.

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c150d3d..8791762 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1294,7 +1294,10 @@ int vsnprintf(char *buf, size_t size, const char *fmt,
va_list args)
                return 0;

        str = buf;
-       end = buf + size;
+       /* LLVM local */
+        end = RELOC_HIDE(buf, size);
+        /* LLVM local end */
+

        /* Make sure end is always >= buf */
        if (end < buf) {

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.