This is a note to let you know that I've just added the patch titled

usb-storage: alauda: Fix uninit-value in alauda_check_media()

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From a6ff6e7a9dd69364547751db0f626a10a6d628d2 Mon Sep 17 00:00:00 2001 From: Alan Stern stern@rowland.harvard.edu Date: Wed, 2 Aug 2023 13:49:02 -0400 Subject: usb-storage: alauda: Fix uninit-value in alauda_check_media()

Syzbot got KMSAN to complain about access to an uninitialized value in the alauda subdriver of usb-storage:

BUG: KMSAN: uninit-value in alauda_transport+0x462/0x57f0 drivers/usb/storage/alauda.c:1137 CPU: 0 PID: 12279 Comm: usb-storage Not tainted 5.3.0-rc7+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x191/0x1f0 lib/dump_stack.c:113 kmsan_report+0x13a/0x2b0 mm/kmsan/kmsan_report.c:108 __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250 alauda_check_media+0x344/0x3310 drivers/usb/storage/alauda.c:460

The problem is that alauda_check_media() doesn't verify that its USB transfer succeeded before trying to use the received data. What should happen if the transfer fails isn't entirely clear, but a reasonably conservative approach is to pretend that no media is present.

A similar problem exists in a usb_stor_dbg() call in alauda_get_media_status(). In this case, when an error occurs the call is redundant, because usb_stor_ctrl_transfer() already will print a debugging message.

Finally, unrelated to the uninitialized memory access, is the fact that alauda_check_media() performs DMA to a buffer on the stack. Fortunately usb-storage provides a general purpose DMA-able buffer for uses like this. We'll use it instead.

Reported-and-tested-by: syzbot+e7d46eb426883fb97efd@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/0000000000007d25ff059457342d@google.com/T/ Suggested-by: Christophe JAILLET christophe.jaillet@wanadoo.fr Signed-off-by: Alan Stern stern@rowland.harvard.edu Fixes: e80b0fade09e ("[PATCH] USB Storage: add alauda support") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/693d5d5e-f09b-42d0-8ed9-1f96cd30bcce@rowland.harva... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/storage/alauda.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/storage/alauda.c b/drivers/usb/storage/alauda.c index 5e912dd29b4c..115f05a6201a 100644 --- a/drivers/usb/storage/alauda.c +++ b/drivers/usb/storage/alauda.c @@ -318,7 +318,8 @@ static int alauda_get_media_status(struct us_data *us, unsigned char *data) rc = usb_stor_ctrl_transfer(us, us->recv_ctrl_pipe, command, 0xc0, 0, 1, data, 2);

- usb_stor_dbg(us, "Media status %02X %02X\n", data[0], data[1]); + if (rc == USB_STOR_XFER_GOOD) + usb_stor_dbg(us, "Media status %02X %02X\n", data[0], data[1]);

return rc; } @@ -454,9 +455,14 @@ static int alauda_init_media(struct us_data *us) static int alauda_check_media(struct us_data *us) { struct alauda_info *info = (struct alauda_info *) us->extra; - unsigned char status[2]; + unsigned char *status = us->iobuf; + int rc;

- alauda_get_media_status(us, status); + rc = alauda_get_media_status(us, status); + if (rc != USB_STOR_XFER_GOOD) { + status[0] = 0xF0; /* Pretend there's no media */ + status[1] = 0; + }

/* Check for no media or door open */ if ((status[0] & 0x80) || ((status[0] & 0x1F) == 0x10)