kexec: ensure user memory sizes do not wrap

Ensure that user memory sizes do not wrap around when validating the
user input, which can lead to the following input validation working
incorrectly.

[[email protected]: fix it for kexec-return-error-number-directly.patch]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Russell King <[email protected]>
Reviewed-by: Pratyush Anand <[email protected]>
Acked-by: Baoquan He <[email protected]>
Cc: Keerthy <[email protected]>
Cc: Vitaly Andrianov <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Simon Horman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/kexec_core.c

@@ -168,6 +168,8 @@ int sanity_check_segment_list(struct kimage *image)
 
 		mstart = image->segment[i].mem;
 		mend   = mstart + image->segment[i].memsz;
+		if (mstart > mend)
+			return -EADDRNOTAVAIL;
 		if ((mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK))
 			return -EADDRNOTAVAIL;
 		if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)