[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>

diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
index 9b8c8a19824de64c9a308177e11f55df3974099c..b48ac635f3c19cb79d11086835b538cc0b1dcf00 100644 (file)
--- 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;
        }
 }