Change in flashrom[master]: dummyflasher.c: Prevent use-after-free bug

[Edward O'Callaghan (Code Review)]

Edward O'Callaghan has submitted this change. ( https://review.coreboot.org/c/flashrom/+/54909 )

Change subject: dummyflasher.c: Prevent use-after-free bug
......................................................................

dummyflasher.c: Prevent use-after-free bug

The memory for the `status` string is aliased by the `endptr` pointer.
Moreover, `errno` could have been modified by the call to `free()`.
Therefore, only free the former when there are no more uses of either.

Change-Id: I1b56834004fe18918213a7df0a09a8a7ecb56985
Signed-off-by: Angel Pons 
Reviewed-on: https://review.coreboot.org/c/flashrom/+/54909
Tested-by: build bot (Jenkins) 
Reviewed-by: Edward O'Callaghan 
Reviewed-by: Anastasia Klimchuk 
---
M dummyflasher.c
1 file changed, 2 insertions(+), 1 deletion(-)

Approvals:
  build bot (Jenkins): Verified
  Edward O'Callaghan: Looks good to me, approved
  Anastasia Klimchuk: Looks good to me, but someone else must approve

diff --git a/dummyflasher.c b/dummyflasher.c
index 5defec0..560dbdc 100644
--- a/dummyflasher.c
+++ b/dummyflasher.c
@@ -962,12 +962,13 @@
    if (status) {
    	errno = 0;
    	data->emu_status = strtoul(status, &endptr, 0);
-		free(status);
    	if (errno != 0 || status == endptr) {
+			free(status);
    		msg_perr("Error: initial status register specified, "
    			 "but the value could not be converted.\n");
    		return 1;
    	}
+		free(status);
    	msg_pdbg("Initial status register is set to 0x%02x.\n",
    		 data->emu_status);
    }