[PATCH 4.19 127/131] usb: f_fs: Clear OS Extended descriptor counts to zero in ffs_data_reset()

[Greg Kroah-Hartman]

From: Udipto Goswami <ugoswami@xxxxxxxxxxxxxx>

commit 1c2e54fbf1da5e5445a0ab132c862b02ccd8d230 upstream.

For userspace functions using OS Descriptors, if a function also supplies
Extended Property descriptors currently the counts and lengths stored in
the ms_os_descs_ext_prop_{count,name_len,data_len} variables are not
getting reset to 0 during an unbind or when the epfiles are closed. If
the same function is re-bound and the descriptors are re-written, this
results in those count/length variables to monotonically increase
causing the VLA allocation in _ffs_func_bind() to grow larger and larger
at each bind/unbind cycle and eventually fail to allocate.

Fix this by clearing the ms_os_descs_ext_prop count & lengths to 0 in
ffs_data_reset().

Fixes: f0175ab51993 ("usb: gadget: f_fs: OS descriptors support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Udipto Goswami <ugoswami@xxxxxxxxxxxxxx>
Signed-off-by: Sriharsha Allenki <sallenki@xxxxxxxxxxxxxx>
Reviewed-by: Manu Gautam <mgautam@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200402044521.9312-1-sallenki@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/gadget/function/f_fs.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1737,6 +1737,10 @@ static void ffs_data_reset(struct ffs_da
 	ffs->state = FFS_READ_DESCRIPTORS;
 	ffs->setup_state = FFS_NO_SETUP;
 	ffs->flags = 0;
+
+	ffs->ms_os_descs_ext_prop_count = 0;
+	ffs->ms_os_descs_ext_prop_name_len = 0;
+	ffs->ms_os_descs_ext_prop_data_len = 0;
 }