From cdafb6d8b8da7fde266f79b3287ac221aa841879 Mon Sep 17 00:00:00 2001
From: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Date: Wed, 8 Nov 2017 10:13:15 -0700
Subject: usb: gadget: f_fs: Fix use-after-free in ffs_free_inst
KASAN enabled configuration reports an error
BUG: KASAN: use-after-free in ffs_free_inst+... [usb_f_fs] at addr ...
Write of size 8 by task ...
This is observed after "ffs-test" is run and interrupted. If after that
functionfs is unmounted and g_ffs module is unloaded, that use-after-free
occurs during g_ffs module removal.
Although the report indicates ffs_free_inst() function, the actual
use-after-free condition occurs in _ffs_free_dev() function, which
is probably inlined into ffs_free_inst().
This happens due to keeping the ffs_data reference in device structure
during functionfs unmounting, while ffs_data itself is freed as no longer
needed. The fix is to clear that reference in ffs_closed() function,
which is a counterpart of ffs_ready(), where the reference is stored.
Fixes: 3262ad824307 ("usb: gadget: f_fs: Stop ffs_closed NULL pointer dereference")
Cc: stable@vger.kernel.org
Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_fs.c | 1 +
1 file changed, 1 insertion(+)
(limited to 'drivers/usb/gadget')
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 6edcf358da01..b1001c3f43fb 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -3673,6 +3673,7 @@ static void ffs_closed(struct ffs_data *ffs)
goto done;
ffs_obj->desc_ready = false;
+ ffs_obj->ffs_data = NULL;
if (test_and_clear_bit(FFS_FL_CALL_CLOSED_CALLBACK, &ffs->flags) &&
ffs_obj->ffs_closed_callback)
--
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