[PATCH RFC 2/4] sh/crash_dump: check ioremap() in copy_oldmem_page()

[Christian Brauner <brauner@kernel.org>]

copy_oldmem_page() maps a page of the old kernel with ioremap() and
copies from it without checking whether the mapping worked. If it
didn't, the copy reads from an offset into the NULL page.

Return -ENOMEM like the other architectures do. read_from_oldmem() turns
that into -EFAULT like any other short copy.

Fixes: 4d5ade5b29c6 ("sh: kdump support.")
Cc: stable@vger.kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 arch/sh/kernel/crash_dump.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/sh/kernel/crash_dump.c b/arch/sh/kernel/crash_dump.c
index 19ce6a950aaca..85c0e58f1a59f 100644
--- a/arch/sh/kernel/crash_dump.c
+++ b/arch/sh/kernel/crash_dump.c
@@ -20,6 +20,9 @@ ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
 		return 0;
 
 	vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
+	if (!vaddr)
+		return -ENOMEM;
+
 	csize = copy_to_iter(vaddr + offset, csize, iter);
 	iounmap(vaddr);
 

-- 
2.53.0