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

[ 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.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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 7df8e3a79dc0cb6b31e7ff9d27f03b2b5949f675..d35d0e4bbf99a6168f2901182115969c316b76bf 100644 (file)
--- 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 df7e07986ead5eae73d37ea980eecfc4a7a8f46c..7ed961c0124f1756ad76f25be21d505e9f6a9f94 100644 (file)
--- 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 d92762286645a90a0fd8bfad21e6860c8f30e0bd..3ffade4f279848ef4de6d7dc40f89357a9298d44 100644 (file)
--- 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,
 };