vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when dumping vsyscall user page

Commit:

  df04abfd181a ("fs/proc/kcore.c: Add bounce buffer for ktext data")

... introduced a bounce buffer to work around CONFIG_HARDENED_USERCOPY=y.
However, accessing the vsyscall user page will cause an SMAP fault.

Replace memcpy() with copy_from_user() to fix this bug works, but adding
a common way to handle this sort of user page may be useful for future.

Currently, only vsyscall page requires KCORE_USER.

Signed-off-by: Jia Zhang <zhang.jia@linux.alibaba.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1518446694-21124-2-git-send-email-zhang.jia@linux.alibaba.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 1ab42c8520693c9999e4b19d04eb565528404ed7..6aa33d1e198f260c1231899d2c683cf78543c3c5 100644 (file)
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1193,8 +1193,7 @@ void __init mem_init(void)
        register_page_bootmem_info();
 
        /* Register memory areas for /proc/kcore */
-       kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR,
-                        PAGE_SIZE, KCORE_OTHER);
+       kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR, PAGE_SIZE, KCORE_USER);
 
        mem_init_print_info(NULL);
 }

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index e8a93bc8285d85403db124f9acb3c80f2a122495..d1e82761de813abb95af0faac99194dba5821538 100644 (file)
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -510,6 +510,10 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
                        /* we have to zero-fill user buffer even if no read */
                        if (copy_to_user(buffer, buf, tsz))
                                return -EFAULT;
+               } else if (m->type == KCORE_USER) {
+                       /* User page is handled prior to normal kernel page: */
+                       if (copy_to_user(buffer, (char *)start, tsz))
+                               return -EFAULT;
                } else {
                        if (kern_addr_valid(start)) {
                                /*

diff --git a/include/linux/kcore.h b/include/linux/kcore.h
index 7ff25a808feffd115e5af4faab56c2542c227c63..80db19d3a5054d5c064727644af49fdf31310111 100644 (file)
--- a/include/linux/kcore.h
+++ b/include/linux/kcore.h
@@ -10,6 +10,7 @@ enum kcore_type {
        KCORE_VMALLOC,
        KCORE_RAM,
        KCORE_VMEMMAP,
+       KCORE_USER,
        KCORE_OTHER,
 };