Messages in this thread Patch in this message | | | Subject | Re: [patch] bug in cpuid & msr on nosmp machine | From | Rusty Russell <> | Date | Thu, 20 May 2004 19:30:01 +1000 |
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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
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