Messages in this thread | | | Date | Sun, 20 Jan 2019 16:20:00 -0500 | From | Scott Bauer <> | Subject | Re: [PATCH v2 11/16] block: sed-opal: ioctl for writing to shadow mbr |
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On Sun, Jan 20, 2019 at 11:27:30AM +0100, David Kozub wrote: > On Sat, 19 Jan 2019, Scott Bauer wrote: > > > On Thu, Jan 17, 2019 at 09:31:51PM +0000, David Kozub wrote: > > > > > +static int write_shadow_mbr(struct opal_dev *dev, void *data) > > > +{ > > > + struct opal_shadow_mbr *shadow = data; > > > + const u8 __user *src; > > > + u8 *dst; > > > + size_t off = 0; > > > + u64 len; > > > + int err = 0; > > > + > > > + /* do the actual transmission(s) */ > > > + src = (u8 *) shadow->data; > > > + while (off < shadow->size) { > > > + err = cmd_start(dev, opaluid[OPAL_MBR], opalmethod[OPAL_SET]); > > > + add_token_u8(&err, dev, OPAL_STARTNAME); > > > + add_token_u8(&err, dev, OPAL_WHERE); > > > + add_token_u64(&err, dev, shadow->offset + off); > > > + add_token_u8(&err, dev, OPAL_ENDNAME); > > > + > > > + add_token_u8(&err, dev, OPAL_STARTNAME); > > > + add_token_u8(&err, dev, OPAL_VALUES); > > > + > > > + /* > > > + * The bytestring header is either 1 or 2 bytes, so assume 2. > > > + * There also needs to be enough space to accommodate the > > > + * trailing OPAL_ENDNAME (1 byte) and tokens added by > > > + * cmd_finalize. > > > + */ > > > + len = min(remaining_size(dev) - (2+1+CMD_FINALIZE_BYTES_NEEDED), > > > + (size_t)(shadow->size - off)); > > > > What if remaining_size(dev) < 2 + 1 + CMD_FINALIZE_BYTES_NEEDED? If that's possible we > > get min(UINT_MAX(ish) , some size larger than our remaining buffer) and that's not good. > > This is only possible for uselessly small values of IO_BUFFER_LENGTH, which > is a compile-time value. Originally I thought it's OK as nobody would set > the value so low. But on a second thought, after reading your comment, I > think that even if IO_BUFFER_LENGTH was set to such a value, the code should > fail gracefully.
Naw, just leave it the way it is. I didnt follow cmd_start down deep enough to realize we reset the position on cmd_start, so there is no way for my scenario to happen. We'll never change IO_BUFFER_LENGTH to something small. If someone wants to write a bug in their custom kernel, it's not our problem.
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