libata debugging: Warn when unable to find timing descriptor based on xfer_mode

ata_timing_find_mode could return NULL which is not checked by all
low-level ATA drivers using it and cause a NULL ptr deref. Warn at least
so that possible issues can get fixed easily.

Signed-off-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 3cc7096cfda7..f46fbd3bd3fb 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2942,6 +2942,10 @@ const struct ata_timing *ata_timing_find_mode(u8 xfer_mode)
 
         if (xfer_mode == t->mode)
                 return t;
+
+        WARN_ONCE(true, "%s: unable to find timing for xfer_mode 0x%x\n",
+                        __func__, xfer_mode);
+
         return NULL;
 }