[PATCH 4.9 041/138] ata: fixes kernel crash while tracing ata_eh_link_autopsy event

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rameshwar Prasad Sahu <rsahu@xxxxxxx>

commit f1601113ddc0339a745e702f4fb1ca37d4875e65 upstream.

When tracing ata link error event, the kernel crashes when the disk is
removed due to NULL pointer access by trace_ata_eh_link_autopsy API.
This occurs as the dev is NULL when the disk disappeared. This patch
fixes this crash by calling trace_ata_eh_link_autopsy only if "dev"
is not NULL.

v2 changes:
 Removed direct passing "link" pointer instead of "dev" in trace API.

Signed-off-by: Rameshwar Prasad Sahu <rsahu@xxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Fixes: 255c03d15a29 ("libata: Add tracepoints")
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/ata/libata-eh.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -2329,8 +2329,8 @@ static void ata_eh_link_autopsy(struct a
 		if (dev->flags & ATA_DFLAG_DUBIOUS_XFER)
 			eflags |= ATA_EFLAG_DUBIOUS_XFER;
 		ehc->i.action |= ata_eh_speed_down(dev, eflags, all_err_mask);
+		trace_ata_eh_link_autopsy(dev, ehc->i.action, all_err_mask);
 	}
-	trace_ata_eh_link_autopsy(dev, ehc->i.action, all_err_mask);
 	DPRINTK("EXIT\n");
 }