linux-kernel - regression from your recent change to x86's copy_user_handle

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Date:	Wed, 22 Apr 2015 07:33:07 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Linus Torvalds" <torvalds@...ux-foundation.org>
Cc:	<linux-kernel@...r.kernel.org>
Subject: regression from your recent change to x86's
 copy_user_handle_tail()

Linus,

while the description of commit cae2a173fe certainly makes sense, the
change itself ignores the __probe_kernel_write() code path, for which
the destination address is expected to be in kernel space but accesses
may still fault. I.e. the use of plain memset() causes
__probe_kernel_write() to oops rather than return an error. Shouldn't
the "(unsigned long)to >= TASK_SIZE_MAX" be relaxed to take the
effect of set_fs() into account?

Thanks, Jan

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