[PATCH v2] x86/platform/efi/efi_64.c: fix a possible hang in efi_ioremap when init_memory_mapping fails.

From: T Makphaibulchoke
Date: Mon Feb 11 2013 - 15:01:23 EST

An attempt to recursively invoke efi_ioremap may cause the kernel to get stuck in an infinite recursive loop.
Calling efi_ioremap with non-page aligned size will eventually, due to
its recursive implementation, call itself with size smaller than a page.
In this case, init_memory_mapping will fail, returning a NULL.
An attempt to recursively invoke efi_ioremap, without checking for a failure,
results in a recursive mapping of an invalid physical address range, 0 to size +
physaddr, causing the kernel to get stuck in an infinite recursive loop.

Here is an example of a hang in the efi_ioremap recursive loop with
efi_ioremap(0x3ff000, 0xfff) call,

[ 69.266517] init_memory_mapping: [mem 0x003ff000-0x003ffffe]
[ 69.267787] init_memory_mapping: [mem 0x00000000-0x003ffffe]
[ 69.268222] [mem 0x00000000-0x001fffff] page 2M
[ 69.268580] [mem 0x00200000-0x003fefff] page 4k
[ 69.268953] init_memory_mapping: [mem 0x003ff000-0x003ffffe]
[ 69.270216] init_memory_mapping: [mem 0x00000000-0x003ffffe]
[ 69.270651] [mem 0x00000000-0x001fffff] page 2M
[ 69.271016] [mem 0x00200000-0x003fefff] page 4k

Signed-off-by: T Makphaibulchoke <tmac@xxxxxx>
arch/x86/platform/efi/efi_64.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 2b20038..4b3e2b0 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -102,6 +102,12 @@ void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size,
return ioremap(phys_addr, size);

last_map_pfn = init_memory_mapping(phys_addr, phys_addr + size);
+ if (!last_map_pfn) {
+ /* Do not try to rmmap again in case of a failure */
+ return NULL;
+ }
if ((last_map_pfn << PAGE_SHIFT) < phys_addr + size) {
unsigned long top = last_map_pfn << PAGE_SHIFT;
efi_ioremap(top, size - (top - phys_addr), type, attribute);

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