From: Catalin Marinas <catalin.marinas@arm.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Chen Huang <chenhuang5@huawei.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Matthew Wilcox <willy@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Randy Dunlap <rdunlap@infradead.org>,
Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-mm <linux-mm@kvack.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [BUG] arm64: an infinite loop in generic_perform_write()
Date: Tue, 6 Jul 2021 18:50:52 +0100 [thread overview]
Message-ID: <20210706175052.GD15218@arm.com> (raw)
In-Reply-To: <7f14271a-9b2f-1afc-3caf-c4e5b36efa73@arm.com>
On Mon, Jun 28, 2021 at 05:22:30PM +0100, Robin Murphy wrote:
> diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S
> index 043da90f5dd7..cfb598ae4812 100644
> --- a/arch/arm64/lib/copy_to_user.S
> +++ b/arch/arm64/lib/copy_to_user.S
> @@ -32,7 +32,7 @@
> .endm
> .macro strh1 reg, ptr, val
> - user_ldst 9998f, sttrh, \reg, \ptr, \val
> + user_ldst 9997f, sttrh, \reg, \ptr, \val
> .endm
> .macro ldr1 reg, ptr, val
> @@ -40,7 +40,7 @@
> .endm
> .macro str1 reg, ptr, val
> - user_ldst 9998f, sttr, \reg, \ptr, \val
> + user_ldst 9997f, sttr, \reg, \ptr, \val
> .endm
> .macro ldp1 reg1, reg2, ptr, val
> @@ -48,12 +48,14 @@
> .endm
> .macro stp1 reg1, reg2, ptr, val
> - user_stp 9998f, \reg1, \reg2, \ptr, \val
> + user_stp 9997f, \reg1, \reg2, \ptr, \val
> .endm
> end .req x5
> +srcin .req x15
> SYM_FUNC_START(__arch_copy_to_user)
> add end, x0, x2
> + mov srcin, x1
> #include "copy_template.S"
> mov x0, #0
> ret
> @@ -62,6 +64,12 @@ EXPORT_SYMBOL(__arch_copy_to_user)
> .section .fixup,"ax"
> .align 2
> +9997: cmp dst, dstin
> + b.ne 9998f
> + // Before being absolutely sure we couldn't copy anything, try harder
> + ldrb tmp1w, [srcin]
> +USER(9998f, sttrb tmp1w, [dstin])
> + add dst, dstin, #1
> 9998: sub x0, end, dst // bytes not copied
> ret
> .previous
I think it's worth doing the copy_to_user() fallback in a loop until it
faults or hits the end of the buffer. This would solve the problem we
currently have with writing more bytes than actually reported. The
copy_from_user() is not necessary, a byte would suffice.
--
Catalin
next prev parent reply other threads:[~2021-07-06 17:51 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-23 2:39 [BUG] arm64: an infinite loop in generic_perform_write() Chen Huang
2021-06-23 2:50 ` Al Viro
2021-06-23 3:24 ` Xiaoming Ni
2021-06-23 4:27 ` Al Viro
2021-06-23 9:32 ` Catalin Marinas
2021-06-23 11:51 ` Matthew Wilcox
2021-06-23 13:04 ` Al Viro
2021-06-23 13:22 ` Mark Rutland
2021-06-24 3:10 ` Chen Huang
2021-06-24 3:24 ` Matthew Wilcox
2021-06-24 3:52 ` Chen Huang
2021-06-24 7:04 ` Christoph Hellwig
2021-06-24 11:15 ` Matthew Wilcox
2021-06-24 13:22 ` Robin Murphy
2021-06-24 16:27 ` Al Viro
2021-06-24 16:38 ` Robin Murphy
2021-06-24 16:39 ` Al Viro
2021-06-24 17:24 ` Robin Murphy
2021-06-24 18:55 ` Catalin Marinas
2021-06-24 20:36 ` Robin Murphy
2021-06-25 10:39 ` Catalin Marinas
2021-06-28 16:22 ` Robin Murphy
2021-06-29 8:30 ` Catalin Marinas
2021-06-29 10:01 ` Robin Murphy
2021-07-06 17:50 ` Catalin Marinas [this message]
2021-07-06 19:15 ` Robin Murphy
2021-07-07 9:55 ` David Laight
2021-07-07 11:04 ` Robin Murphy
2021-07-07 12:50 ` Catalin Marinas
2021-06-24 15:09 ` Catalin Marinas
2021-06-24 16:17 ` Al Viro
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