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From: Al Viro <viro@zeniv.linux.org.uk>
To: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 11/20] amifb: get rid of pointless access_ok() calls
Date: Thu, 14 May 2020 18:41:31 +0100	[thread overview]
Message-ID: <20200514174131.GD23230@ZenIV.linux.org.uk> (raw)
In-Reply-To: <f6fcfa46-6271-45ea-37c2-62bcf0a607cb@samsung.com>

On Thu, May 14, 2020 at 04:25:35PM +0200, Bartlomiej Zolnierkiewicz wrote:
> Thank you for in-detail explanations, for this patch:
> 
> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> 
> Could you also please take care of adding missing checks for {get,put}_user()
> failures later?

Umm...  OK; put_user() side is trivial -  the interesting part is what to do
about get_user() failures halfway through.  Right now it treats them as
"we'd read zeroes".  On anything else I would say "screw it, memdup_user()
the damn thing on the way in and copy from there", but... Amiga has how
much RAM, again?

OTOH, from my reading of that code it does appear to be limited to
4Kb of data to copy, so it's probably OK...  Hell knows - I'm really
confused by those #ifdef __mc68000__ in there; the driver *is*
amiga-only:
obj-$(CONFIG_FB_AMIGA)            += amifb.o c2p_planar.o
config FB_AMIGA
        tristate "Amiga native chipset support"
        depends on FB && AMIGA
and AMIGA is defined only in arch/m68k/Kconfig.machine.  So how the
hell can it *not* be true?  OTOH, it looks like hand-optimized
asm equivalents of C they have in #else, so that #else might be
meant to document what's going on...

I've no idea how to test any changes to that thing - the only
m68k emulator I'm reasonably familiar with is aranym, and
that's Atari, not Amiga.  Never got around to setting up UAE...
So I can do a patch more or less blindly (memdup_user() after
it has checked the limits on height/width, then dereferencing
from copy instead of get_user()), but I won't be able to test
it.

  reply	other threads:[~2020-05-14 17:41 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09 23:41 [PATCHES] uaccess simple access_ok() removals Al Viro
2020-05-09 23:45 ` [PATCH 01/20] dlmfs_file_write(): get rid of pointless access_ok() Al Viro
2020-05-09 23:45   ` [PATCH 02/20] fat_dir_ioctl(): hadn't needed that access_ok() for more than a decade Al Viro
2020-05-09 23:45   ` [PATCH 03/20] btrfs_ioctl_send(): don't bother with access_ok() Al Viro
2020-05-09 23:45   ` [PATCH 04/20] FIEMAP: " Al Viro
2020-05-10  7:02     ` Christoph Hellwig
2020-05-13 19:02       ` Al Viro
2020-05-13 19:38         ` Christoph Hellwig
2020-05-29 15:01           ` Al Viro
2020-05-09 23:45   ` [PATCH 05/20] tomoyo_write_control(): get rid of pointless access_ok() Al Viro
2020-05-10  0:50     ` Tetsuo Handa
2020-05-10  0:57       ` Linus Torvalds
2020-05-10  1:04         ` Tetsuo Handa
2020-05-10  3:01         ` Al Viro
2020-05-09 23:45   ` [PATCH 06/20] n_hdlc_tty_read(): remove " Al Viro
2020-05-15 10:53     ` Greg Kroah-Hartman
2020-05-09 23:45   ` [PATCH 07/20] nvram: drop useless access_ok() Al Viro
2020-05-15 10:54     ` Greg Kroah-Hartman
2020-05-09 23:45   ` [PATCH 08/20] cm4000_cs.c cmm_ioctl(): get rid of pointless access_ok() Al Viro
2020-05-09 23:45   ` [PATCH 09/20] drivers/fpga/dfl-fme-pr.c: " Al Viro
2020-05-09 23:45   ` [PATCH 10/20] drivers/fpga/dfl-afu-dma-region.c: " Al Viro
2020-05-09 23:45   ` [PATCH 11/20] amifb: get rid of pointless access_ok() calls Al Viro
2020-05-14 13:45     ` Bartlomiej Zolnierkiewicz
2020-05-14 14:07       ` Al Viro
2020-05-14 14:25         ` Bartlomiej Zolnierkiewicz
2020-05-14 17:41           ` Al Viro [this message]
2020-05-14 20:21             ` Geert Uytterhoeven
2020-05-09 23:45   ` [PATCH 12/20] omapfb: " Al Viro
2020-05-14 13:39     ` Bartlomiej Zolnierkiewicz
2020-05-09 23:45   ` [PATCH 13/20] drivers/crypto/ccp/sev-dev.c: get rid of pointless access_ok() Al Viro
2020-05-09 23:45   ` [PATCH 14/20] via-pmu: don't bother with access_ok() Al Viro
2020-05-09 23:45   ` [PATCH 15/20] drm_read(): get rid of pointless access_ok() Al Viro
2020-05-09 23:45   ` [PATCH 16/20] efi_test: " Al Viro
2020-05-09 23:45   ` [PATCH 17/20] lpfc_debugfs: " Al Viro
2020-05-09 23:45   ` [PATCH 18/20] usb: get rid of pointless access_ok() calls Al Viro
2020-05-15 10:53     ` Greg Kroah-Hartman
2020-05-09 23:45   ` [PATCH 19/20] hfi1: get rid of pointless access_ok() Al Viro
2020-05-09 23:45   ` [PATCH 4/4] vmci_host: " Al Viro
2020-05-15 10:53     ` Greg Kroah-Hartman
2020-05-10  0:34 ` [PATCHES] uaccess simple access_ok() removals Linus Torvalds
2020-05-10  3:27   ` Al Viro
2020-05-10 14:34 ` David Laight

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