From: Kees Cook <keescook@chromium.org>
Date: Tue, 20 Sep 2022 21:13:05 +0000 (-0700)
Subject: coredump: Proactively round up to kmalloc bucket size
X-Git-Tag: v6.6.17~5838^2~26
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6dd142d9013ca82155d0c069434c60a0d5755ec0;p=platform%2Fkernel%2Flinux-rpi.git

coredump: Proactively round up to kmalloc bucket size

Instead of discovering the kmalloc bucket size _after_ allocation, round
up proactively so the allocation is explicitly made for the full size,
allowing the compiler to correctly reason about the resulting size of
the buffer through the existing __alloc_size() hint.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---

diff --git a/fs/coredump.c b/fs/coredump.c
index 7bad778..97eaee32 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -68,7 +68,10 @@ struct core_name {
 
 static int expand_corename(struct core_name *cn, int size)
 {
-	char *corename = krealloc(cn->corename, size, GFP_KERNEL);
+	char *corename;
+
+	size = kmalloc_size_roundup(size);
+	corename = krealloc(cn->corename, size, GFP_KERNEL);
 
 	if (!corename)
 		return -ENOMEM;
@@ -76,7 +79,7 @@ static int expand_corename(struct core_name *cn, int size)
 	if (size > core_name_size) /* racy but harmless */
 		core_name_size = size;
 
-	cn->size = ksize(corename);
+	cn->size = size;
 	cn->corename = corename;
 	return 0;
 }