[patch 043/146] gup: avoid multiple user access locking/unlocking in fault_in_{read/write}able

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Subject: gup: avoid multiple user access locking/unlocking in fault_in_{read/write}able

fault_in_readable() and fault_in_writeable() perform __get_user() and
__put_user() in a loop, implying multiple user access locking/unlocking.

To avoid that, use user access blocks.

Link: https://lkml.kernel.org/r/720dcf79314acca1a78fae56d478cc851952149d.1637084492.git.christophe.leroy@xxxxxxxxxx
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Reviewed-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/gup.c |   18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

--- a/mm/gup.c~gup-avoid-multiple-user-access-locking-unlocking-in-fault_in_read-writeable
+++ a/mm/gup.c
@@ -1672,21 +1672,22 @@ size_t fault_in_writeable(char __user *u
 
 	if (unlikely(size == 0))
 		return 0;
+	if (!user_write_access_begin(uaddr, size))
+		return size;
 	if (!PAGE_ALIGNED(uaddr)) {
-		if (unlikely(__put_user(0, uaddr) != 0))
-			return size;
+		unsafe_put_user(0, uaddr, out);
 		uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr);
 	}
 	end = (char __user *)PAGE_ALIGN((unsigned long)start + size);
 	if (unlikely(end < start))
 		end = NULL;
 	while (uaddr != end) {
-		if (unlikely(__put_user(0, uaddr) != 0))
-			goto out;
+		unsafe_put_user(0, uaddr, out);
 		uaddr += PAGE_SIZE;
 	}
 
 out:
+	user_write_access_end();
 	if (size > uaddr - start)
 		return size - (uaddr - start);
 	return 0;
@@ -1771,21 +1772,22 @@ size_t fault_in_readable(const char __us
 
 	if (unlikely(size == 0))
 		return 0;
+	if (!user_read_access_begin(uaddr, size))
+		return size;
 	if (!PAGE_ALIGNED(uaddr)) {
-		if (unlikely(__get_user(c, uaddr) != 0))
-			return size;
+		unsafe_get_user(c, uaddr, out);
 		uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr);
 	}
 	end = (const char __user *)PAGE_ALIGN((unsigned long)start + size);
 	if (unlikely(end < start))
 		end = NULL;
 	while (uaddr != end) {
-		if (unlikely(__get_user(c, uaddr) != 0))
-			goto out;
+		unsafe_get_user(c, uaddr, out);
 		uaddr += PAGE_SIZE;
 	}
 
 out:
+	user_read_access_end();
 	(void)c;
 	if (size > uaddr - start)
 		return size - (uaddr - start);
_



[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux