Messages in this thread | | | From | Arnd Bergmann <> | Date | Wed, 4 Dec 2019 15:05:09 +0100 | Subject | Re: [GIT PULL] first round of SCSI updates for the 5.4+ merge window |
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On Mon, Dec 2, 2019 at 10:58 PM Linus Torvalds <torvalds@linux-foundation.org> wrote: > > Anyway, the sg copyin/out changes by Al conflicted fairly badly with > Arnd's compat_ioctl changes. > > Al did > > c35a5cfb4150 ("scsi: sg: sg_read(): simplify reading ->pack_id of > userland sg_io_hdr_t") > > which avoided doing a whole allocation of an 'sg_io_hdr_t' to just > read the one field of it. > > But Arnd did > > 98aaaec4a150 ("compat_ioctl: reimplement SG_IO handling") > > which created a get_sg_io_hdr() helper that copied the 'sg_io_hdr_t' > from user space the right way for both compat and native, which > basically relied on the old approach.
Right, I also failed to notice that the linux-next conflict resolution was breaking my changes, the fixup looked simple enough there. :-(
> since it turns out that the one 'pack_id' field we want does have the > same format in compat mode as in native mode ("int" and > "compat_int_t" are the same), it's just at different offsets. But the > definition of 'compat_sg_io_hdr' isn't available in that place. > > I'm leaving it to Al and Arnd to decide if they want to fix the > stupidity. I tried to make the minimally invasive merge resolution. > > Al, Arnd? Comments? > > It looks like linux-next punted on this entirely, and took Al's > simplified version that doesn't work with the compat case. Maybe I > should have done the same - if you use read() on the /dev/sg* device, > you deserve to get broken for the compat case. And it didn't > historically work anyway. But it was kind of sad to see how Arnd fixed > it, and then it got broken again.
I've tried now to move the pack_id logic into a separate function and, in doing so noticed a bug in my own patch: sg_new_read() needs to check for the compat_sg_io_hdr size, which also depends on the struct definition. I've drafted a patch that should do this right, but we could also just -EINVAL in compat mode here if that's too complex.
Arnd
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