Re: [REGRESSION] usb: gadget: f_fs: Allow scatter-gather buffers

[Andrzej Pietrasiewicz]

Hi John,

W dniu 08.05.2019 oÂ04:18, John Stultz pisze:
> Since commit 772a7a724f69 ("usb: gadget: f_fs: Allow scatter-gather
> buffers"), I've been seeing trouble with adb transfers in Android on
> HiKey960, HiKey and now Dragonboard 845c.
>
> Sometimes things crash, but often the transfers just stop w/o any
> obvious error messages.

<snip>

> Andrzej: Do you have any ideas or suggestions on this? I'm happy to
> test or run any debug patches, if it would help narrow the issue down.

Can you please try the below patch?

One more thing to consider is "functionfs read size 512 > requested size 24,
splitting request into multiple reads." in your original report, but let's
try this first:

From f2b8f27cfa42cafe1f56d8abbe2c76fa0072e368 Mon Sep 17 00:00:00 2001
From: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>
Date: Wed, 8 May 2019 13:52:40 +0200
Subject: [PATCH] usb: gadget: Zero ffs_io_data

In some cases the "Allocate & copy" block in ffs_epfile_io() is not
executed. Consequently, in such a case ffs_alloc_buffer() is never called
and struct ffs_io_data is not initialized properly. This in turn leads to
problems when ffs_free_buffer() is called at the end of ffs_epfile_io().

This patch uses kzalloc() instead of kmalloc() in the aio case and memset()
in non-aio case to properly initialize struct ffs_io_data.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>
---
 drivers/usb/gadget/function/f_fs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 47be961f1bf3..41d57ae8bc15 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1182,11 +1182,12 @@ static ssize_t ffs_epfile_write_iter(struct kiocb 
*kiocb, struct iov_iter *from)
 	ENTER();

 	if (!is_sync_kiocb(kiocb)) {
-		p = kmalloc(sizeof(io_data), GFP_KERNEL);
+		p = kzalloc(sizeof(io_data), GFP_KERNEL);
 		if (unlikely(!p))
 			return -ENOMEM;
 		p->aio = true;
 	} else {
+		memset(p, 0, sizeof(*p));
 		p->aio = false;
 	}

@@ -1218,11 +1219,12 @@ static ssize_t ffs_epfile_read_iter(struct kiocb *kiocb, 
struct iov_iter *to)
 	ENTER();

 	if (!is_sync_kiocb(kiocb)) {
-		p = kmalloc(sizeof(io_data), GFP_KERNEL);
+		p = kzalloc(sizeof(io_data), GFP_KERNEL);
 		if (unlikely(!p))
 			return -ENOMEM;
 		p->aio = true;
 	} else {
+		memset(p, 0, sizeof(*p));
 		p->aio = false;
 	}

--
2.17.1