This is a note to let you know that I've just added the patch titled
usb: gadget: ncm: Fix handling of zero block length packets
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-gadget-ncm-fix-handling-of-zero-block-length-packets.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f90ce1e04cbcc76639d6cba0fdbd820cd80b3c70 Mon Sep 17 00:00:00 2001
From: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
Date: Wed, 28 Feb 2024 17:24:41 +0530
Subject: usb: gadget: ncm: Fix handling of zero block length packets
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From: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
commit f90ce1e04cbcc76639d6cba0fdbd820cd80b3c70 upstream.
While connecting to a Linux host with CDC_NCM_NTB_DEF_SIZE_TX
set to 65536, it has been observed that we receive short packets,
which come at interval of 5-10 seconds sometimes and have block
length zero but still contain 1-2 valid datagrams present.
According to the NCM spec:
"If wBlockLength = 0x0000, the block is terminated by a
short packet. In this case, the USB transfer must still
be shorter than dwNtbInMaxSize or dwNtbOutMaxSize. If
exactly dwNtbInMaxSize or dwNtbOutMaxSize bytes are sent,
and the size is a multiple of wMaxPacketSize for the
given pipe, then no ZLP shall be sent.
wBlockLength= 0x0000 must be used with extreme care, because
of the possibility that the host and device may get out of
sync, and because of test issues.
wBlockLength = 0x0000 allows the sender to reduce latency by
starting to send a very large NTB, and then shortening it when
the sender discovers that there’s not sufficient data to justify
sending a large NTB"
However, there is a potential issue with the current implementation,
as it checks for the occurrence of multiple NTBs in a single
giveback by verifying if the leftover bytes to be processed is zero
or not. If the block length reads zero, we would process the same
NTB infintely because the leftover bytes is never zero and it leads
to a crash. Fix this by bailing out if block length reads zero.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 427694cfaafa ("usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call")
Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
Reviewed-by: Maciej Żenczykowski <maze@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240228115441.2105585-1-quic_kriskura@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/gadget/function/f_ncm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -1357,7 +1357,7 @@ parse_ntb:
if (to_process == 1 &&
(*(unsigned char *)(ntb_ptr + block_len) == 0x00)) {
to_process--;
- } else if (to_process > 0) {
+ } else if ((to_process > 0) && (block_len != 0)) {
ntb_ptr = (unsigned char *)(ntb_ptr + block_len);
goto parse_ntb;
}
Patches currently in stable-queue which might be from quic_kriskura@xxxxxxxxxxx are
queue-4.19/usb-gadget-ncm-fix-handling-of-zero-block-length-packets.patch
