linux-kernel - RE: [PATCHES] uaccess simple access

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Message-ID: <847a5160e4e64a82962dc1531cd52e11@AcuMS.aculab.com>
Date:   Sun, 10 May 2020 14:34:04 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Al Viro' <viro@...iv.linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCHES] uaccess simple access_ok() removals

From: Al Viro
> Sent: 10 May 2020 00:41
> 
> 	One of the uaccess-related branches; this one is just the
> cases when access_ok() calls are trivially pointless - the address
> in question gets fed only to primitives that do access_ok() checks
> themselves.

There is also the check in rw_copy_check_uvector() that should
always be replicated by the copy_to/from_user() in _copy_to/from_iter().

And the strange call to rw_copy_check_uvector() in mm/process_vm_access.c
which carefully avoids the access_ok() check for the target process.
I did a quick look, but failed to see an obvious check further
down the call path.
The code is doing a read/write from another process, not sure when it
is used - not by gdb.

	David

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