From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaly Kuznetsov Subject: [PATCH] efi: fix for_each_efi_memory_desc_in_map() for empty memmaps Date: Wed, 25 May 2016 16:36:55 +0200 Message-ID: <1464187015-5640-1-git-send-email-vkuznets@redhat.com> Return-path: Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Matt Fleming , "K. Y. Srinivasan" List-Id: linux-efi@vger.kernel.org Commit 78ce248faa3c ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()") introduced a regression for systems booted with 'noefi' kernel option. In particular, I observe early kernel hang in efi_find_mirror() on for_each_efi_memory_desc() call. As we don't have efi memmap we enter this iterator with the following parameters: efi.memmap.map = 0, efi.memmap.map_end = 0, efi.memmap.desc_size = 28 for_each_efi_memory_desc_in_map() does the following comparison: (md) <= (efi_memory_desc_t *)((m)->map_end - (m)->desc_size); where md = 0, (m)->map_end = 0 and (m)->desc_size = 28 but when we subtract something from a NULL pointer wrap around happens and we end up returning invalid pointer. Fixes: 78ce248faa3c ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()") Signed-off-by: Vitaly Kuznetsov --- include/linux/efi.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/efi.h b/include/linux/efi.h index c2db3ca..229ccb5 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1005,7 +1005,8 @@ extern int efi_memattr_apply_permissions(struct mm_struct *mm, /* Iterate through an efi_memory_map */ #define for_each_efi_memory_desc_in_map(m, md) \ for ((md) = (m)->map; \ - (md) <= (efi_memory_desc_t *)((m)->map_end - (m)->desc_size); \ + (efi_memory_desc_t *)((md) + (m)->desc_size) <= \ + (efi_memory_desc_t *)(m)->map_end; \ (md) = (void *)(md) + (m)->desc_size) /** -- 2.5.5