x86/KASLR: Fix boot crash with certain memory configurations

Baoquan He · Ingo Molnar · commit 6daa2ec0b3e3 · 2016-07-08T14:36:19.000+02:00
Ye Xiaolong reported this boot crash:

|
|  XZ-compressed data is corrupt
|
|   -- System halted
|

Fix the bug in mem_avoid_overlap() of finding the earliest overlap.

Reported-and-tested-by: Ye Xiaolong &lt;xiaolong.ye@intel.com&gt;
Signed-off-by: Baoquan He &lt;bhe@redhat.com&gt;
Cc: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
@@ -285,6 +285,7 @@ static bool mem_avoid_overlap(struct mem_vector *img,
 		if (mem_overlaps(img, &mem_avoid[i]) &&
 		    mem_avoid[i].start < earliest) {
 			*overlap = mem_avoid[i];
+			earliest = overlap->start;
 			is_overlapping = true;
 		}
 	}
@@ -299,6 +300,7 @@ static bool mem_avoid_overlap(struct mem_vector *img,
 
 		if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) {
 			*overlap = avoid;
+			earliest = overlap->start;
 			is_overlapping = true;
 		}
 

Original file line number	Diff line number	Diff line change
`@@ -285,6 +285,7 @@ static bool mem_avoid_overlap(struct mem_vector *img,`
`285`	`285`	`if (mem_overlaps(img, &mem_avoid[i]) &&`
`286`	`286`	`mem_avoid[i].start < earliest) {`
`287`	`287`	`*overlap = mem_avoid[i];`
	`288`	`+ earliest = overlap->start;`
`288`	`289`	`is_overlapping = true;`
`289`	`290`	`}`
`290`	`291`	`}`
`@@ -299,6 +300,7 @@ static bool mem_avoid_overlap(struct mem_vector *img,`
`299`	`300`
`300`	`301`	`if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) {`
`301`	`302`	`*overlap = avoid;`
	`303`	`+ earliest = overlap->start;`
`302`	`304`	`is_overlapping = true;`
`303`	`305`	`}`
`304`	`306`