diff mbox

fcntl: don't cap l_start and l_end values for F_GETLK64 in compat syscall

Message ID 20171115131750.27717-1-jlayton@kernel.org (mailing list archive)
State New, archived
Headers show

Commit Message

Jeff Layton Nov. 15, 2017, 1:17 p.m. UTC 
From: Jeff Layton <jlayton@redhat.com>

Currently, we're capping the values too low in the F_GETLK64 case. The
fields in that structure are 64-bit values, so we shouldn't need to any
sort of fixup there.

Make sure we check that assumption at build time in the future however
by ensuring that the sizes we're copying will fit.

Fixes: 94073ad77fff2 (fs/locks: don't mess with the address limit in compat_fcntl64)
Reported-by: Vitaly Lipatov <lav@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/fcntl.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

Comments

Vitaly Lipatov Nov. 15, 2017, 1:36 p.m. UTC | #1 
Jeff Layton писал 15.11.17 16:17:
> From: Jeff Layton <jlayton@redhat.com>
> 
> Currently, we're capping the values too low in the F_GETLK64 case. The
> fields in that structure are 64-bit values, so we shouldn't need to any
> sort of fixup there.
> 
> Make sure we check that assumption at build time in the future however
> by ensuring that the sizes we're copying will fit.
Nice fix.
The only question I do not know answer is what is purpose of 
COMPAT_LOFF_T_MAX macro?
diff mbox

Patch

diff --git a/fs/fcntl.c b/fs/fcntl.c
index e15bcc4265d0..0522e283a4f4 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -563,6 +563,9 @@  static int put_compat_flock64(const struct flock *kfl, struct compat_flock64 __u
 {
 	struct compat_flock64 fl;
 
+	BUILD_BUG_ON(sizeof(kfl->l_start) > sizeof(ufl->l_start));
+	BUILD_BUG_ON(sizeof(kfl->l_len) > sizeof(ufl->l_len));
+
 	memset(&fl, 0, sizeof(struct compat_flock64));
 	copy_flock_fields(&fl, kfl);
 	if (copy_to_user(ufl, &fl, sizeof(struct compat_flock64)))
@@ -641,12 +644,8 @@  COMPAT_SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 		if (err)
 			break;
 		err = fcntl_getlk(f.file, convert_fcntl_cmd(cmd), &flock);
-		if (err)
-			break;
-		err = fixup_compat_flock(&flock);
-		if (err)
-			return err;
-		err = put_compat_flock64(&flock, compat_ptr(arg));
+		if (!err)
+			err = put_compat_flock64(&flock, compat_ptr(arg));
 		break;
 	case F_SETLK:
 	case F_SETLKW: