[PATCH] fixup bogus e820 entry with mem=

This was reported because someone was getting oopses reading /proc/iomem.
It was tracked down to a zero-sized 'struct resource' entry which was
located right at 4GB.

You need two conditions to hit this bug: a BIOS E820_RAM area starting at
exactly the boundary where you specify mem= (to get a zero-sized entry),
and for the legacy_init_iomem_resources() loop to skip that resource (which
only happens at exactly 4G).

I think the killing zero-sized e820 entry is the easiest way to fix this.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 17 insertions, 7 deletions

diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
index 9b8c8a19824d..b48ac635f3c1 100644
--- a/arch/i386/kernel/setup.c
+++ b/arch/i386/kernel/setup.c
@@ -389,14 +389,24 @@ static void __init limit_regions(unsigned long long size)
                 }
         }
         for (i = 0; i < e820.nr_map; i++) {
-                if (e820.map[i].type == E820_RAM) {
-                        current_addr = e820.map[i].addr + e820.map[i].size;
-                        if (current_addr >= size) {
-                                e820.map[i].size -= current_addr-size;
-                                e820.nr_map = i + 1;
-                                return;
-                        }
+                current_addr = e820.map[i].addr + e820.map[i].size;
+                if (current_addr < size)
+                        continue;
+
+                if (e820.map[i].type != E820_RAM)
+                        continue;
+
+                if (e820.map[i].addr >= size) {
+                        /*
+                         * This region starts past the end of the
+                         * requested size, skip it completely.
+                         */
+                        e820.nr_map = i;
+                } else {
+                        e820.nr_map = i + 1;
+                        e820.map[i].size -= current_addr - size;
                 }
+                return;
         }
 }