From: Jia Zhang <zhang....@linux.alibaba.com>

[ Upstream commit 595dd46ebfc10be041a365d0a3fa99df50b6ba73 ]

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....@linux.alibaba.com>
Reviewed-by: Jiri Olsa <jo...@kernel.org>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: jo...@redhat.com
Link: 
http://lkml.kernel.org/r/1518446694-21124-2-git-send-email-zhang....@linux.alibaba.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 arch/x86/mm/init_64.c | 3 +--
 fs/proc/kcore.c       | 4 ++++
 include/linux/kcore.h | 1 +
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 7df8e3a79dc0..d35d0e4bbf99 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1014,8 +1014,7 @@ void __init mem_init(void)
        after_bootmem = 1;
 
        /* 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 df7e07986ead..7ed961c0124f 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -505,6 +505,10 @@ 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 d92762286645..3ffade4f2798 100644
--- a/include/linux/kcore.h
+++ b/include/linux/kcore.h
@@ -9,6 +9,7 @@ enum kcore_type {
        KCORE_VMALLOC,
        KCORE_RAM,
        KCORE_VMEMMAP,
+       KCORE_USER,
        KCORE_OTHER,
 };
 
-- 
2.15.1

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