x86/KASLR: Handle kernel relocations above 2G correctly

When processing the relocation table, the offset used to calculate the
relocation is an 'int'. This is sufficient for calculating the physical
address of the relocs entry on 32-bit systems and on 64-bit systems when
the relocation is under 2G.

To handle relocations above 2G (seen in situations like kexec, netboot, etc),
this offset needs to be calculated using a 'long' to avoid wrapping and
miscalculating the relocation.

Signed-off-by: Baoquan He <bhe@redhat.com>
[ Rewrote the changelog. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: lasse.collin@tukaani.org
Link: http://lkml.kernel.org/r/1461888548-32439-2-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 6dde6ccdf00ebcee7472a89887795f5da9e3b3bf..45145149c07d5d8ad7aae1154d4e9bc55f9b50dd 100644 (file)
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -232,7 +232,7 @@ static void handle_relocations(void *output, unsigned long output_len)
         * So we work backwards from the end of the decompressed image.
         */
        for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
-               int extended = *reloc;
+               long extended = *reloc;
                extended += map;
 
                ptr = (unsigned long)extended;