Hello/
On pátek 28. července 2023 17:26:11 CEST David Laight wrote:
> From: Oleksandr Natalenko
> > Sent: 28 July 2023 07:58
> >
> > The qedf_dbg_debug_cmd_read() function invokes sprintf()
> > directly on a __user pointer, which may crash the kernel.
> ^^^ will
I don't think it is 100% guaranteed, but for sure this is not a correct behaviour.
> >
> > Avoid doing that by using a small on-stack buffer for sprintf()
> > and then calling simple_read_from_buffer() which does a proper
> > copy_to_user() call.
> ...
> > diff --git a/drivers/scsi/qedf/qedf_debugfs.c b/drivers/scsi/qedf/qedf_debugfs.c
> > index 4d1b99569d490..f910af0029a2c 100644
> > --- a/drivers/scsi/qedf/qedf_debugfs.c
> > +++ b/drivers/scsi/qedf/qedf_debugfs.c
> > @@ -138,15 +138,14 @@ qedf_dbg_debug_cmd_read(struct file *filp, char __user *buffer, size_t count,
> > loff_t *ppos)
> > {
> > int cnt;
> > + char cbuf[35];
>
> Why 35?
> I pick a multiple of 8 that if 'enough.
OK, I overestimated this, it should have been 27, but I'll make it 32 to be a multiple of 8.
Thanks.
> > struct qedf_dbg_ctx *qedf_dbg =
> > (struct qedf_dbg_ctx *)filp->private_data;
> >
> > QEDF_INFO(qedf_dbg, QEDF_LOG_DEBUGFS, "debug mask=0x%x\n", qedf_debug);
> > - cnt = sprintf(buffer, "debug mask = 0x%x\n", qedf_debug);
> > + cnt = sprintf(cbuf, "debug mask = 0x%x\n", qedf_debug);
>
> Use scnprintf() to be sure it doesn't overflow.
> Much safer if someone does a quick update or copies the code.
>
> David
>
> >
> > - cnt = min_t(int, count, cnt - *ppos);
> > - *ppos += cnt;
> > - return cnt;
> > + return simple_read_from_buffer(buffer, count, ppos, cbuf, cnt);
> > }
> >
> > static ssize_t
> > --
> > 2.41.0
>
> -
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>
>
--
Oleksandr Natalenko (post-factum)
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