From ffc8599aa9763f39f6736a79da4d1575e7006f9a Mon Sep 17 00:00:00 2001 From: Kairui Song Date: Fri, 8 Mar 2019 11:05:08 +0800 Subject: [PATCH] x86/gart: Exclude GART aperture from kcore On machines where the GART aperture is mapped over physical RAM, /proc/kcore contains the GART aperture range. Accessing the GART range via /proc/kcore results in a kernel crash. vmcore used to have the same issue, until it was fixed with commit 2a3e83c6f96c ("x86/gart: Exclude GART aperture from vmcore")', leveraging existing hook infrastructure in vmcore to let /proc/vmcore return zeroes when attempting to read the aperture region, and so it won't read from the actual memory. Apply the same workaround for kcore. First implement the same hook infrastructure for kcore, then reuse the hook functions introduced in the previous vmcore fix. Just with some minor adjustment, rename some functions for more general usage, and simplify the hook infrastructure a bit as there is no module usage yet. Suggested-by: Baoquan He Signed-off-by: Kairui Song Signed-off-by: Thomas Gleixner Reviewed-by: Jiri Bohac Acked-by: Baoquan He Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: Alexey Dobriyan Cc: Andrew Morton Cc: Omar Sandoval Cc: Dave Young Link: https://lkml.kernel.org/r/20190308030508.13548-1-kasong@redhat.com --- arch/x86/kernel/aperture_64.c | 20 +++++++++++++------- fs/proc/kcore.c | 27 +++++++++++++++++++++++++++ include/linux/kcore.h | 2 ++ 3 files changed, 42 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c index 58176b56354e..294ed4392a0e 100644 --- a/arch/x86/kernel/aperture_64.c +++ b/arch/x86/kernel/aperture_64.c @@ -14,6 +14,7 @@ #define pr_fmt(fmt) "AGP: " fmt #include +#include #include #include #include @@ -57,7 +58,7 @@ int fallback_aper_force __initdata; int fix_aperture __initdata = 1; -#ifdef CONFIG_PROC_VMCORE +#if defined(CONFIG_PROC_VMCORE) || defined(CONFIG_PROC_KCORE) /* * If the first kernel maps the aperture over e820 RAM, the kdump kernel will * use the same range because it will remain configured in the northbridge. @@ -66,20 +67,25 @@ int fix_aperture __initdata = 1; */ static unsigned long aperture_pfn_start, aperture_page_count; -static int gart_oldmem_pfn_is_ram(unsigned long pfn) +static int gart_mem_pfn_is_ram(unsigned long pfn) { return likely((pfn < aperture_pfn_start) || (pfn >= aperture_pfn_start + aperture_page_count)); } -static void exclude_from_vmcore(u64 aper_base, u32 aper_order) +static void __init exclude_from_core(u64 aper_base, u32 aper_order) { aperture_pfn_start = aper_base >> PAGE_SHIFT; aperture_page_count = (32 * 1024 * 1024) << aper_order >> PAGE_SHIFT; - WARN_ON(register_oldmem_pfn_is_ram(&gart_oldmem_pfn_is_ram)); +#ifdef CONFIG_PROC_VMCORE + WARN_ON(register_oldmem_pfn_is_ram(&gart_mem_pfn_is_ram)); +#endif +#ifdef CONFIG_PROC_KCORE + WARN_ON(register_mem_pfn_is_ram(&gart_mem_pfn_is_ram)); +#endif } #else -static void exclude_from_vmcore(u64 aper_base, u32 aper_order) +static void exclude_from_core(u64 aper_base, u32 aper_order) { } #endif @@ -474,7 +480,7 @@ out: * may have allocated the range over its e820 RAM * and fixed up the northbridge */ - exclude_from_vmcore(last_aper_base, last_aper_order); + exclude_from_core(last_aper_base, last_aper_order); return 1; } @@ -520,7 +526,7 @@ out: * overlap with the first kernel's memory. We can't access the * range through vmcore even though it should be part of the dump. */ - exclude_from_vmcore(aper_alloc, aper_order); + exclude_from_core(aper_alloc, aper_order); /* Fix up the north bridges */ for (i = 0; i < amd_nb_bus_dev_ranges[i].dev_limit; i++) { diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index bbcc185062bb..d29d869abec1 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -54,6 +54,28 @@ static LIST_HEAD(kclist_head); static DECLARE_RWSEM(kclist_lock); static int kcore_need_update = 1; +/* + * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error + * Same as oldmem_pfn_is_ram in vmcore + */ +static int (*mem_pfn_is_ram)(unsigned long pfn); + +int __init register_mem_pfn_is_ram(int (*fn)(unsigned long pfn)) +{ + if (mem_pfn_is_ram) + return -EBUSY; + mem_pfn_is_ram = fn; + return 0; +} + +static int pfn_is_ram(unsigned long pfn) +{ + if (mem_pfn_is_ram) + return mem_pfn_is_ram(pfn); + else + return 1; +} + /* This doesn't grab kclist_lock, so it should only be used at init time. */ void __init kclist_add(struct kcore_list *new, void *addr, size_t size, int type) @@ -465,6 +487,11 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) goto out; } m = NULL; /* skip the list anchor */ + } else if (!pfn_is_ram(__pa(start) >> PAGE_SHIFT)) { + if (clear_user(buffer, tsz)) { + ret = -EFAULT; + goto out; + } } else if (m->type == KCORE_VMALLOC) { vread(buf, (char *)start, tsz); /* we have to zero-fill user buffer even if no read */ diff --git a/include/linux/kcore.h b/include/linux/kcore.h index 8c3f8c14eeaa..c843f4a9c512 100644 --- a/include/linux/kcore.h +++ b/include/linux/kcore.h @@ -44,6 +44,8 @@ void kclist_add_remap(struct kcore_list *m, void *addr, void *vaddr, size_t sz) m->vaddr = (unsigned long)vaddr; kclist_add(m, addr, sz, KCORE_REMAP); } + +extern int __init register_mem_pfn_is_ram(int (*fn)(unsigned long pfn)); #else static inline void kclist_add(struct kcore_list *new, void *addr, size_t size, int type)