[PATCH AUTOSEL for 4.15 181/189] vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when dumping vsyscall user page

[Sasha Levin]

From: Jia Zhang <zhang.jia@xxxxxxxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxxxx>
Reviewed-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: jolsa@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1518446694-21124-2-git-send-email-zhang.jia@xxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 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 60ae1fe3609f..780097ed24ea 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1186,8 +1186,7 @@ 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 e8a93bc8285d..d1e82761de81 100644
--- 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 7ff25a808fef..80db19d3a505 100644
--- 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,
 };
 
-- 
2.15.1