From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Stephen Boyd <stephen.boyd@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Punit Agrawal <punit.agrawal@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: traps: Mark __le16, __le32, __user variables properly
Date: Fri, 17 Feb 2017 17:31:01 +0000 [thread overview]
Message-ID: <20170217173101.GH21222@n2100.armlinux.org.uk> (raw)
In-Reply-To: <20170217165112.17512-1-stephen.boyd@linaro.org>
On Fri, Feb 17, 2017 at 08:51:12AM -0800, Stephen Boyd wrote:
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 659b2e6b6cf7..23959cb70ded 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -84,7 +84,7 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
> if (p >= bottom && p < top) {
> unsigned long val;
>
> - if (__get_user(val, (unsigned long *)p) == 0)
> + if (__get_user(val, (unsigned long __user *)p) == 0)
> sprintf(str + i * 17, " %016lx", val);
> else
> sprintf(str + i * 17, " ????????????????");
> @@ -113,7 +113,7 @@ static void __dump_instr(const char *lvl, struct pt_regs *regs)
> for (i = -4; i < 1; i++) {
> unsigned int val, bad;
>
> - bad = __get_user(val, &((u32 *)addr)[i]);
> + bad = __get_user(val, &((u32 __user *)addr)[i]);
>
> if (!bad)
> p += sprintf(p, i == 0 ? "(%08x) " : "%08x ", val);
> @@ -340,23 +340,28 @@ static int call_undef_hook(struct pt_regs *regs)
> return 1;
>
> if (compat_thumb_mode(regs)) {
> + __le16 tinst;
> +
> /* 16-bit Thumb instruction */
> - if (get_user(instr, (u16 __user *)pc))
> + if (get_user(tinst, (__le16 __user *)pc))
> goto exit;
> - instr = le16_to_cpu(instr);
> + instr = le16_to_cpu(tinst);
> if (aarch32_insn_is_wide(instr)) {
> - u32 instr2;
> + __le16 tinstr2;
> + u16 instr2;
>
> - if (get_user(instr2, (u16 __user *)(pc + 2)))
> + if (get_user(tinstr2, (__le16 __user *)(pc + 2)))
> goto exit;
> - instr2 = le16_to_cpu(instr2);
> + instr2 = le16_to_cpu(tinstr2);
> instr = (instr << 16) | instr2;
> }
> } else {
> + __le32 ainst;
> +
> /* 32-bit ARM instruction */
> - if (get_user(instr, (u32 __user *)pc))
> + if (get_user(ainst, (__le32 __user *)pc))
> goto exit;
> - instr = le32_to_cpu(instr);
> + instr = le32_to_cpu(ainst);
For the majority of causes, these are _not_ user addresses, they are
kernel addresses. The use of get_user() at these locations is a way
to safely access these kernel addresses when something has gone wrong
without causing a further oops.
Annotating them with __user to shut up sparse is incorrect. The point
with sparse is _not_ to end up with a warning free kernel, but for it
to warn where things are not quite right in terms of semantics. These
warnings should stay.
So, the warnings about lack of __user should stay.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2017-02-17 17:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-17 16:51 Stephen Boyd
2017-02-17 17:31 ` Russell King - ARM Linux [this message]
2017-02-19 1:58 ` Luc Van Oostenryck
[not found] ` <148758047729.2988.16966413648865610904@sboyd-linaro>
2017-02-20 10:04 ` Luc Van Oostenryck
2017-02-20 10:49 ` Mark Rutland
2017-02-20 21:33 ` Luc Van Oostenryck
2017-02-21 11:03 ` Will Deacon
2017-02-22 13:00 ` Luc Van Oostenryck
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