From: Rusty Russell <rusty@rustcorp.com.au>
To: Andrew Morton <akpm@osdl.org>
Cc: castet.matthieu@free.fr,
lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [patch] bug in cpuid & msr on nosmp machine
Date: Thu, 20 May 2004 19:30:01 +1000 [thread overview]
Message-ID: <1085045400.7541.32.camel@bach> (raw)
In-Reply-To: <20040520015142.0ca69add.akpm@osdl.org>
On Thu, 2004-05-20 at 18:51, Andrew Morton wrote:
> How about this?
Complicated *and* doesn't solve the original problem.
How about this?
Name: Fix i386/x86_64 cpuid/msr BUG() on Impossible CPUs
Status: Trivial
Matthieu Castet <castet.matthieu@free.fr> pointed out that testing
cpu_online(cpu) on a UP system goes BUG().
That's because you're never supposed to ask cpu_online() about a CPU
which is >= NR_CPUS. msr and cpuid devices use the minor to indicate
the CPU number. Oops.
Fix is to explicitly test cpu < NR_CPUS. Using cpu_online() is OK;
although the CPU might go down before you actually read the file, that
will simply cause junk to be returned.
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .7878-linux-2.6.6-bk6/arch/i386/kernel/cpuid.c .7878-linux-2.6.6-bk6.updated/arch/i386/kernel/cpuid.c
--- .7878-linux-2.6.6-bk6/arch/i386/kernel/cpuid.c 2004-05-20 10:35:22.000000000 +1000
+++ .7878-linux-2.6.6-bk6.updated/arch/i386/kernel/cpuid.c 2004-05-20 19:26:47.000000000 +1000
@@ -132,10 +132,10 @@ static ssize_t cpuid_read(struct file *f
static int cpuid_open(struct inode *inode, struct file *file)
{
- int cpu = iminor(file->f_dentry->d_inode);
+ unsigned int cpu = iminor(file->f_dentry->d_inode);
struct cpuinfo_x86 *c = &(cpu_data)[cpu];
- if (!cpu_online(cpu))
+ if (cpu >= NR_CPUS || !cpu_online(cpu))
return -ENXIO; /* No such CPU */
if (c->cpuid_level < 0)
return -EIO; /* CPUID not supported */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .7878-linux-2.6.6-bk6/arch/i386/kernel/msr.c .7878-linux-2.6.6-bk6.updated/arch/i386/kernel/msr.c
--- .7878-linux-2.6.6-bk6/arch/i386/kernel/msr.c 2004-02-18 23:54:12.000000000 +1100
+++ .7878-linux-2.6.6-bk6.updated/arch/i386/kernel/msr.c 2004-05-20 19:27:01.000000000 +1000
@@ -238,10 +238,10 @@ static ssize_t msr_write(struct file * f
static int msr_open(struct inode *inode, struct file *file)
{
- int cpu = iminor(file->f_dentry->d_inode);
+ unsigned int cpu = iminor(file->f_dentry->d_inode);
struct cpuinfo_x86 *c = &(cpu_data)[cpu];
- if (!cpu_online(cpu))
+ if (cpu >= NR_CPUS || !cpu_online(cpu))
return -ENXIO; /* No such CPU */
if ( !cpu_has(c, X86_FEATURE_MSR) )
return -EIO; /* MSR not supported */
--
Anyone who quotes me in their signature is an idiot -- Rusty Russell
next prev parent reply other threads:[~2004-05-20 9:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-19 16:35 [patch] bug in cpuid & msr on nosmp machine matthieu castet
2004-05-19 17:46 ` matthieu castet
2004-05-20 2:44 ` Jeff Sipek
2004-05-20 9:51 ` Paul Jackson
2004-05-20 7:32 ` Andrew Morton
2004-05-20 8:34 ` Rusty Russell
2004-05-20 8:51 ` Andrew Morton
2004-05-20 9:30 ` Rusty Russell [this message]
2004-05-20 9:57 ` Rusty Russell
[not found] <1XCh4-1jO-67@gated-at.bofh.it>
[not found] ` <1XRg3-4LW-31@gated-at.bofh.it>
[not found] ` <1XRg3-4LW-29@gated-at.bofh.it>
[not found] ` <1XSc3-5y3-23@gated-at.bofh.it>
2004-05-22 8:13 ` Andi Kleen
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