[Crash-utility] [PATCH] diskdump: fix read_diskdump() returns successfully for illegal 0-size page descriptors

[HATAYAMA Daisuke]

read_diskdump() returns successfully for illegal 0-size page
descriptors. Page descriptors are illegal if their size member holds 0
because makedumpfile never puts 0 there because any data never result
in 0 byte by compression. If page descriptors hold 0 in size member,
it means the crash dump file is corrupted for some reason.

The root cause of this is that sanity check of function cache_page()
doesn't focus on such 0-size page descriptors. Then, the 0-size page
descriptor is passed to pread(), pread() immediately returns 0
successfully because read data is 0 byte, and then read_diskdump()
returns successfully.

To fix this issue, let the sanity check take into account such 0-size
page descriptors and read_diskdump() result in READ_ERROR.

Signed-off-by: HATAYAMA Daisuke <d.hatayama at fujitsu.com>
---
 diskdump.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/diskdump.c b/diskdump.c
index 2c284ff..2be7cc7 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -1210,7 +1210,7 @@ cache_page(physaddr_t paddr)
 		return ret;
 
 	/* sanity check */
-	if (pd.size > block_size)
+	if (pd.size > block_size || !pd.size)
 		return READ_ERROR;
 
 	/* read page data */
-- 
2.25.1