Commit 7ca97c61 authored by Robert Hentosh's avatar Robert Hentosh Committed by Linus Torvalds
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[PATCH] x86_64: Fix off by one in bad_addr checking in find_e820_area

From: Robert Hentosh <>

Actually, we just stumbled on a different bug found in find_e820_area() in
e820.c.  The following code does not handle the edge condition correctly:

   while (bad_addr(&addr, size) && addr+size < ei->addr + ei->size)
   last = addr + size;
   if ( last > ei->addr + ei->size )

The second statement in the while loop needs to be a <= b so that it is the
logical negavite of the if (a > b) outside it. It needs to read:

   while (bad_addr(&addr, size) && addr+size <= ei->addr + ei->size)

In the case that failed bad_addr was returning an address that is exactly size
bellow the end of the e820 range.

AK: Again together with the earlier avoid edma fix this fixes
boot on a Dell PE6850/16GB
Signed-off-by: default avatarAndi Kleen <>
Signed-off-by: default avatarLinus Torvalds <>
parent 0d015324
......@@ -149,7 +149,7 @@ unsigned long __init find_e820_area(unsigned long start, unsigned long end, unsi
addr = start;
if (addr > ei->addr + ei->size)
while (bad_addr(&addr, size) && addr+size < ei->addr + ei->size)
while (bad_addr(&addr, size) && addr+size <= ei->addr+ei->size)
last = addr + size;
if (last > ei->addr + ei->size)
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