From: David Howells <dhowells@redhat.com>
Subject: Guard check in module loader against integer overflow
Date: Tue, 22 May 2012 15:56:13 +0100

The check:

	if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr))

may not work if there's an overflow in the right-hand side of the condition.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 kernel/module.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/module.c b/kernel/module.c
index 78ac6ec..377cb06 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2429,7 +2429,8 @@ static int copy_and_check(struct load_info *info,
 		goto free_hdr;
 	}
 
-	if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr)) {
+	if (hdr->e_shoff >= len ||
+	    hdr->e_shnum * sizeof(Elf_Shdr) > len - hdr->e_shoff) {
 		err = -ENOEXEC;
 		goto free_hdr;
 	}