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: [PATCH] usb-storage: alauda: Fix uninit-value in alauda_check_media()
Git-commit: a6ff6e7a9dd69364547751db0f626a10a6d628d2
References: git-fixes
Patch-mainline: v6.5-rc6
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.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
drivers/usb/storage/alauda.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/drivers/usb/storage/alauda.c
+++ b/drivers/usb/storage/alauda.c
@@ -330,7 +330,8 @@ static int alauda_get_media_status(struc
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;
}
@@ -466,10 +467,14 @@ static int alauda_init_media(struct us_d
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;
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)