[PATCH 2/2] pstore: Add buffer start check during init

[Mukesh Ojha]

From: Huang Yiwei <hyiwei@xxxxxxxxxxxxxx>

In a scenario of panic, when we use DRAM to store log instead
of persistant storage and during warm reset when we copy these
data outside of ram. Missing check on prz->start(write position)
can cause crash because it can be any value and can point outside
the mapped region. So add the start check to avoid.

Signed-off-by: Huang Yiwei <hyiwei@xxxxxxxxxxxxxx>
Signed-off-by: Mukesh Ojha <mojha@xxxxxxxxxxxxxx>
---
change in v2:
 - this is on top of first patchset.

 fs/pstore/ram_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index 0da012f..a15748a 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -514,7 +514,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
 	sig ^= PERSISTENT_RAM_SIG;
 
 	if (prz->buffer->sig == sig) {
-		if (buffer_size(prz) == 0) {
+		if (buffer_size(prz) == 0 && buffer_start(prz) == 0) {
 			pr_debug("found existing empty buffer\n");
 			return 0;
 		}
-- 
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