lkml.org 
[lkml]   [2017]   [Feb]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] arm64: traps: Mark __le16, __le32, __user variables properly
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.

\
 
 \ /
  Last update: 2017-02-17 18:31    [W:0.108 / U:0.728 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site