thunderbolt: Fix double free of drom buffer

If tb_drom_read() fails, sw->drom is freed but not set to NULL.  sw->drom
is then freed again in the error path of tb_switch_alloc().

The bug can be triggered by unplugging a thunderbolt device shortly after
it is detected by the thunderbolt driver.

Clear sw->drom if tb_drom_read() fails.

[bhelgaas: add Fixes:, stable versions of interest]
Fixes: 343fcb8c70d7 ("thunderbolt: Fix nontrivial endpoint devices.")
Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v3.17+
CC: Lukas Wunner <lukas@wunner.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
index 0c052e25c5bc..2b9602c2c355 100644
--- a/drivers/thunderbolt/eeprom.c
+++ b/drivers/thunderbolt/eeprom.c
@@ -449,6 +449,7 @@ int tb_drom_read(struct tb_switch *sw)
         return tb_drom_parse_entries(sw);
 err:
         kfree(sw->drom);
+        sw->drom = NULL;
         return -EIO;
 
 }