Messages in this thread | | | Subject | Re: [PATCH RESEND] scsi: sg: Prevent potential double frees in sg driver | From | Douglas Gilbert <> | Date | Tue, 2 Oct 2018 09:34:33 +1000 |
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On 2018-10-02 02:15 AM, Evan Green wrote: > From: Robb Glasser <rglasser@google.com> > > sg_ioctl could be spammed by requests, leading to a double free in > __free_pages. This protects the entry points of sg_ioctl where the > memory could be corrupted by a double call to __free_pages if multiple > requests are happening concurrently.
Hi, I don't like this patch. I would like to see the trace for the double call to the __free_pages you are referring too. A test program that show the fault, perhaps?
I have test code to "spam" the sg driver and have not seen a double __free_pages that you refer to (see sg3_utils package version 1.44, testing/sg_tst_async.cpp).
Currently I am dusting off 20 years of "laparoscopic" patches to the sg driver that have made a bit of a mess of the naming and comments. Also the 16 outstanding requests per file descriptor limit is being removed. Then I want to add the SG_IOSUBMIT and SG_IORECEIVE ioctls proposed by Linus Torvalds two week ago.
Executive summary: nak, without further information
Doug Gilbert
> Signed-off-by: Robb Glasser <rglasser@google.com> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > Signed-off-by: Evan Green <evgreen@chromium.org> > Cc: stable@vger.kernel.org > > --- > Reposting this patch from last summer, as it looks like it fell in between > the cracks. > > drivers/scsi/sg.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > index 8a254bb46a9b..25579d8a16b5 100644 > --- a/drivers/scsi/sg.c > +++ b/drivers/scsi/sg.c > @@ -924,8 +924,10 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) > return -ENXIO; > if (!access_ok(VERIFY_WRITE, p, SZ_SG_IO_HDR)) > return -EFAULT; > + mutex_lock(&sfp->parentdp->open_rel_lock); > result = sg_new_write(sfp, filp, p, SZ_SG_IO_HDR, > 1, read_only, 1, &srp); > + mutex_unlock(&sfp->parentdp->open_rel_lock); > if (result < 0) > return result; > result = wait_event_interruptible(sfp->read_wait, >
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