Messages in this thread | | | Date | Wed, 29 Dec 2021 10:16:22 +0100 | Subject | Re: KMSAN: uninit-value in alauda_check_media | From | Christophe JAILLET <> |
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Le 28/12/2021 à 23:49, Alan Stern a écrit : > On Tue, Dec 28, 2021 at 08:47:15AM +0100, Christophe JAILLET wrote: >> Hi, >> >> (2nd try - text only format - sorry for the noise) >> >> >> first try to use syzbot. I hope I do it right. >> Discussion about the syz report can be found at >> https://lore.kernel.org/linux-kernel/0000000000007d25ff059457342d@google.com/ >> >> This patch only test if alauda_get_media_status() (and its embedded >> usb_stor_ctrl_transfer()) before using the data. >> In case of error, it returns USB_STOR_TRANSPORT_ERROR as done elsewhere. >> >> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git >> master >> >> CJ >> > >> diff --git a/drivers/usb/storage/alauda.c b/drivers/usb/storage/alauda.c >> index 20b857e97e60..6c486d964911 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]); > > Instead of adding this test, you could initialize data[0] and data[1] > to zero before the call to usb_stor_ctrl_transfer.
Well, having the test is cleaner, IMHO. If usb_stor_ctrl_transfer() fails, a message explaining the reason is already generated by the same usb_stor_dbg(). Having an error message followed by another one stating that the Media Status is 0x00 0x00 could be confusing I think.
Let me know if you have a real preference for a memset(data, 0, 2). If so, I'll add it.
> >> >> return rc; >> } >> @@ -453,8 +454,11 @@ static int alauda_check_media(struct us_data *us) >> { >> struct alauda_info *info = (struct alauda_info *) us->extra; >> unsigned char status[2]; >> + int rc; >> >> - alauda_get_media_status(us, status); >> + rc = alauda_get_media_status(us, status); >> + if (rc != USB_STOR_TRANSPORT_GOOD) >> + return USB_STOR_TRANSPORT_ERROR; >> >> /* Check for no media or door open */ >> if ((status[0] & 0x80) || ((status[0] & 0x1F) == 0x10) > > In general this looks fine. Let us know when you are ready to submit > the patch.
I was unsure that this patch would get any interest because the driver looks old. That's why I first tried to play with syzbot :)
In the syzbot history, you also mentioned that 'unsigned char status[2]' should be 'unsigned char *status = us->iobuf;'
This is more a blind fix for me, but it looks consistent with other places that call alauda_get_media_status().
So, once you confirm if you prefer my 'if' or a 'memset', I'll resend a small serie for fixing both issues.
CJ
> > Alan Stern >
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