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

[Sriharsha Allenki <sallenki@codeaurora.org>]

From: Udipto Goswami <ugoswami@codeaurora.org>

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().

Change-Id: I3b292fe5386ab54b53df2b9f15f07430dc3df24a
Fixes: f0175ab51993 ("usb: gadget: f_fs: OS descriptors support")
Cc: stable@vger.kernel.org
Signed-off-by: Udipto Goswami <ugoswami@codeaurora.org>
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>
---
 drivers/usb/gadget/function/f_fs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index c81023b195c3..10f01f974f67 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1813,6 +1813,10 @@ static void ffs_data_reset(struct ffs_data *ffs)
 	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;
 }
 
 
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