rewrite file locking compat syscalls

rewrite file locking compat syscalls

[Christoph Hellwig]

Export proper lowlevel helper and use them from the compat code instead
of playing set_fs games.

[PATCH 1/2] fs/locks: pass kernel struct flock to fcntl_getlk/setlk

[Christoph Hellwig]

This will make it easier to implement a sane compat fcntl syscall.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/fcntl.c         | 26 ++++++++++++++----
 fs/locks.c         | 77 +++++++++++++++---------------------------------------
 include/linux/fs.h |  8 +++---
 3 files changed, 46 insertions(+), 65 deletions(-)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index f4e7267d117f..671ac43c65df 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -246,6 +246,8 @@ static int f_getowner_uids(struct file *filp, unsigned long arg)
 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 		struct file *filp)
 {
+	void __user *argp = (void __user *)arg;
+	struct flock flock;
 	long err = -EINVAL;
 
 	switch (cmd) {
@@ -273,7 +275,11 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 	case F_OFD_GETLK:
 #endif
 	case F_GETLK:
-		err = fcntl_getlk(filp, cmd, (struct flock __user *) arg);
+		if (copy_from_user(&flock, argp, sizeof(flock)))
+			return -EFAULT;
+		err = fcntl_getlk(filp, cmd, &flock);
+		if (!err && copy_to_user(argp, &flock, sizeof(flock)))
+			return -EFAULT;
 		break;
 #if BITS_PER_LONG != 32
 	/* 32-bit arches must use fcntl64() */
@@ -283,7 +289,9 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 		/* Fallthrough */
 	case F_SETLK:
 	case F_SETLKW:
-		err = fcntl_setlk(fd, filp, cmd, (struct flock __user *) arg);
+		if (copy_from_user(&flock, argp, sizeof(flock)))
+			return -EFAULT;
+		err = fcntl_setlk(fd, filp, cmd, &flock);
 		break;
 	case F_GETOWN:
 		/*
@@ -384,6 +392,7 @@ SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 		unsigned long, arg)
 {	
 	struct fd f = fdget_raw(fd);
+	struct flock64 flock;
 	long err = -EBADF;
 
 	if (!f.file)
@@ -401,14 +410,21 @@ SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 	switch (cmd) {
 	case F_GETLK64:
 	case F_OFD_GETLK:
-		err = fcntl_getlk64(f.file, cmd, (struct flock64 __user *) arg);
+		err = -EFAULT;
+		if (copy_from_user(&flock, argp, sizeof(flock)))
+			break;
+		err = fcntl_getlk64(filp, cmd, &flock);
+		if (!err && copy_to_user(argp, &flock, sizeof(flock)))
+			err = -EFAULT;
 		break;
 	case F_SETLK64:
 	case F_SETLKW64:
 	case F_OFD_SETLK:
 	case F_OFD_SETLKW:
-		err = fcntl_setlk64(fd, f.file, cmd,
-				(struct flock64 __user *) arg);
+		err = -EFAULT;
+		if (copy_from_user(&flock, argp, sizeof(flock)))
+			break;
+		err = fcntl_setlk64(fd, f.file, cmd, &flock);
 		break;
 	default:
 		err = do_fcntl(fd, cmd, arg, f.file);
diff --git a/fs/locks.c b/fs/locks.c
index af2031a1fcff..054f6fb7641e 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2086,26 +2086,22 @@ static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
 /* Report the first existing lock that would conflict with l.
  * This implements the F_GETLK command of fcntl().
  */
-int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock __user *l)
+int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
 {
 	struct file_lock file_lock;
-	struct flock flock;
 	int error;
 
-	error = -EFAULT;
-	if (copy_from_user(&flock, l, sizeof(flock)))
-		goto out;
 	error = -EINVAL;
-	if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
+	if (flock->l_type != F_RDLCK && flock->l_type != F_WRLCK)
 		goto out;
 
-	error = flock_to_posix_lock(filp, &file_lock, &flock);
+	error = flock_to_posix_lock(filp, &file_lock, flock);
 	if (error)
 		goto out;
 
 	if (cmd == F_OFD_GETLK) {
 		error = -EINVAL;
-		if (flock.l_pid != 0)
+		if (flock->l_pid != 0)
 			goto out;
 
 		cmd = F_GETLK;
@@ -2117,15 +2113,12 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock __user *l)
 	if (error)
 		goto out;
  
-	flock.l_type = file_lock.fl_type;
+	flock->l_type = file_lock.fl_type;
 	if (file_lock.fl_type != F_UNLCK) {
-		error = posix_lock_to_flock(&flock, &file_lock);
+		error = posix_lock_to_flock(flock, &file_lock);
 		if (error)
 			goto rel_priv;
 	}
-	error = -EFAULT;
-	if (!copy_to_user(l, &flock, sizeof(flock)))
-		error = 0;
 rel_priv:
 	locks_release_private(&file_lock);
 out:
@@ -2218,26 +2211,16 @@ check_fmode_for_setlk(struct file_lock *fl)
  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
  */
 int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
-		struct flock __user *l)
+		struct flock *flock)
 {
 	struct file_lock *file_lock = locks_alloc_lock();
-	struct flock flock;
-	struct inode *inode;
+	struct inode *inode = locks_inode(filp);
 	struct file *f;
 	int error;
 
 	if (file_lock == NULL)
 		return -ENOLCK;
 
-	inode = locks_inode(filp);
-
-	/*
-	 * This might block, so we do it before checking the inode.
-	 */
-	error = -EFAULT;
-	if (copy_from_user(&flock, l, sizeof(flock)))
-		goto out;
-
 	/* Don't allow mandatory locks on files that may be memory mapped
 	 * and shared.
 	 */
@@ -2246,7 +2229,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
 		goto out;
 	}
 
-	error = flock_to_posix_lock(filp, file_lock, &flock);
+	error = flock_to_posix_lock(filp, file_lock, flock);
 	if (error)
 		goto out;
 
@@ -2261,7 +2244,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
 	switch (cmd) {
 	case F_OFD_SETLK:
 		error = -EINVAL;
-		if (flock.l_pid != 0)
+		if (flock->l_pid != 0)
 			goto out;
 
 		cmd = F_SETLK;
@@ -2270,7 +2253,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
 		break;
 	case F_OFD_SETLKW:
 		error = -EINVAL;
-		if (flock.l_pid != 0)
+		if (flock->l_pid != 0)
 			goto out;
 
 		cmd = F_SETLKW;
@@ -2315,26 +2298,22 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
 /* Report the first existing lock that would conflict with l.
  * This implements the F_GETLK command of fcntl().
  */
-int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l)
+int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
 {
 	struct file_lock file_lock;
-	struct flock64 flock;
 	int error;
 
-	error = -EFAULT;
-	if (copy_from_user(&flock, l, sizeof(flock)))
-		goto out;
 	error = -EINVAL;
-	if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
+	if (flock->l_type != F_RDLCK && flock->l_type != F_WRLCK)
 		goto out;
 
-	error = flock64_to_posix_lock(filp, &file_lock, &flock);
+	error = flock64_to_posix_lock(filp, &file_lock, flock);
 	if (error)
 		goto out;
 
 	if (cmd == F_OFD_GETLK) {
 		error = -EINVAL;
-		if (flock.l_pid != 0)
+		if (flock->l_pid != 0)
 			goto out;
 
 		cmd = F_GETLK64;
@@ -2348,11 +2327,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l)
 
 	flock.l_type = file_lock.fl_type;
 	if (file_lock.fl_type != F_UNLCK)
-		posix_lock_to_flock64(&flock, &file_lock);
-
-	error = -EFAULT;
-	if (!copy_to_user(l, &flock, sizeof(flock)))
-		error = 0;
+		posix_lock_to_flock64(flock, &file_lock);
 
 	locks_release_private(&file_lock);
 out:
@@ -2363,26 +2338,16 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l)
  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
  */
 int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
-		struct flock64 __user *l)
+		struct flock64 *flock)
 {
 	struct file_lock *file_lock = locks_alloc_lock();
-	struct flock64 flock;
-	struct inode *inode;
+	struct inode *inode = locks_inode(filp);
 	struct file *f;
 	int error;
 
 	if (file_lock == NULL)
 		return -ENOLCK;
 
-	/*
-	 * This might block, so we do it before checking the inode.
-	 */
-	error = -EFAULT;
-	if (copy_from_user(&flock, l, sizeof(flock)))
-		goto out;
-
-	inode = locks_inode(filp);
-
 	/* Don't allow mandatory locks on files that may be memory mapped
 	 * and shared.
 	 */
@@ -2391,7 +2356,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
 		goto out;
 	}
 
-	error = flock64_to_posix_lock(filp, file_lock, &flock);
+	error = flock64_to_posix_lock(filp, file_lock, flock);
 	if (error)
 		goto out;
 
@@ -2406,7 +2371,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
 	switch (cmd) {
 	case F_OFD_SETLK:
 		error = -EINVAL;
-		if (flock.l_pid != 0)
+		if (flock->l_pid != 0)
 			goto out;
 
 		cmd = F_SETLK64;
@@ -2415,7 +2380,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
 		break;
 	case F_OFD_SETLKW:
 		error = -EINVAL;
-		if (flock.l_pid != 0)
+		if (flock->l_pid != 0)
 			goto out;
 
 		cmd = F_SETLKW64;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 803e5a9b2654..aa4affb38c39 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1038,14 +1038,14 @@ static inline struct inode *locks_inode(const struct file *f)
 }
 
 #ifdef CONFIG_FILE_LOCKING
-extern int fcntl_getlk(struct file *, unsigned int, struct flock __user *);
+extern int fcntl_getlk(struct file *, unsigned int, struct flock *);
 extern int fcntl_setlk(unsigned int, struct file *, unsigned int,
-			struct flock __user *);
+			struct flock *);
 
 #if BITS_PER_LONG == 32
-extern int fcntl_getlk64(struct file *, unsigned int, struct flock64 __user *);
+extern int fcntl_getlk64(struct file *, unsigned int, struct flock64 *);
 extern int fcntl_setlk64(unsigned int, struct file *, unsigned int,
-			struct flock64 __user *);
+			struct flock64 *);
 #endif
 
 extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg);
-- 
2.11.0

[PATCH 2/2] fs/locks: don't mess with the address limit in compat_fcntl64

[Christoph Hellwig]

Instead write a proper compat syscall that calls common helpers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/fcntl.c | 118 +++++++++++++++++++++++++++++++++++--------------------------
 fs/locks.c |   2 +-
 2 files changed, 68 insertions(+), 52 deletions(-)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 671ac43c65df..9d909b029063 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -505,76 +505,92 @@ convert_fcntl_cmd(unsigned int cmd)
 	return cmd;
 }
 
+/*
+ * GETLK was successful and we need to return the data, but it needs to fit in
+ * the compat structure.
+ * l_start shouldn't be too big, unless the original start + end is greater than
+ * COMPAT_OFF_T_MAX, in which case the app was asking for trouble, so we return
+ * -EOVERFLOW in that case.  l_len could be too big, in which case we just
+ * truncate it, and only allow the app to see that part of the conflicting lock
+ * that might make sense to it anyway
+ */
+static int fixup_compat_flock(struct flock *flock)
+{
+	if (flock.l_start > COMPAT_OFF_T_MAX)
+		return -EOVERFLOW;
+	if (flock.l_len > COMPAT_OFF_T_MAX)
+		flock.l_len = COMPAT_OFF_T_MAX;
+	return 0;
+}
+
 COMPAT_SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
 		       compat_ulong_t, arg)
 {
-	mm_segment_t old_fs;
-	struct flock f;
-	long ret;
-	unsigned int conv_cmd;
+	struct fd f = fdget_raw(fd);
+	struct flock flock;
+	long err = -EBADF;
+
+	if (!f.file)
+		return err;
+
+	if (unlikely(f.file->f_mode & FMODE_PATH)) {
+		if (!check_fcntl_cmd(cmd))
+			goto out_put;
+	}
+
+	err = security_file_fcntl(f.file, cmd, arg);
+	if (err)
+		goto out_put;
 
 	switch (cmd) {
 	case F_GETLK:
+		err = get_compat_flock(&flock, compat_ptr(arg));
+		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_flock(&flock, compat_ptr(arg));
+		break;
+	case F_GETLK64:
+	case F_OFD_GETLK:
+		err = get_compat_flock64(&flock, compat_ptr(arg));
+		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));
+		break;
 	case F_SETLK:
 	case F_SETLKW:
-		ret = get_compat_flock(&f, compat_ptr(arg));
-		if (ret != 0)
+		err = get_compat_flock(&flock, compat_ptr(arg));
+		if (err)
 			break;
-		old_fs = get_fs();
-		set_fs(KERNEL_DS);
-		ret = sys_fcntl(fd, cmd, (unsigned long)&f);
-		set_fs(old_fs);
-		if (cmd == F_GETLK && ret == 0) {
-			/* GETLK was successful and we need to return the data...
-			 * but it needs to fit in the compat structure.
-			 * l_start shouldn't be too big, unless the original
-			 * start + end is greater than COMPAT_OFF_T_MAX, in which
-			 * case the app was asking for trouble, so we return
-			 * -EOVERFLOW in that case.
-			 * l_len could be too big, in which case we just truncate it,
-			 * and only allow the app to see that part of the conflicting
-			 * lock that might make sense to it anyway
-			 */
-
-			if (f.l_start > COMPAT_OFF_T_MAX)
-				ret = -EOVERFLOW;
-			if (f.l_len > COMPAT_OFF_T_MAX)
-				f.l_len = COMPAT_OFF_T_MAX;
-			if (ret == 0)
-				ret = put_compat_flock(&f, compat_ptr(arg));
-		}
+		err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
 		break;
-
-	case F_GETLK64:
 	case F_SETLK64:
 	case F_SETLKW64:
-	case F_OFD_GETLK:
 	case F_OFD_SETLK:
 	case F_OFD_SETLKW:
-		ret = get_compat_flock64(&f, compat_ptr(arg));
-		if (ret != 0)
+		err = get_compat_flock64(&flock, compat_ptr(arg));
+		if (err)
 			break;
-		old_fs = get_fs();
-		set_fs(KERNEL_DS);
-		conv_cmd = convert_fcntl_cmd(cmd);
-		ret = sys_fcntl(fd, conv_cmd, (unsigned long)&f);
-		set_fs(old_fs);
-		if ((conv_cmd == F_GETLK || conv_cmd == F_OFD_GETLK) && ret == 0) {
-			/* need to return lock information - see above for commentary */
-			if (f.l_start > COMPAT_LOFF_T_MAX)
-				ret = -EOVERFLOW;
-			if (f.l_len > COMPAT_LOFF_T_MAX)
-				f.l_len = COMPAT_LOFF_T_MAX;
-			if (ret == 0)
-				ret = put_compat_flock64(&f, compat_ptr(arg));
-		}
+		err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
 		break;
-
 	default:
-		ret = sys_fcntl(fd, cmd, arg);
+		err = do_fcntl(fd, cmd, arg, f.file);
 		break;
 	}
-	return ret;
+out_put:
+	fdput(f);
+	return err;
 }
 
 COMPAT_SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd,
diff --git a/fs/locks.c b/fs/locks.c
index 054f6fb7641e..8b4e78e4c054 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2325,7 +2325,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
 	if (error)
 		goto out;
 
-	flock.l_type = file_lock.fl_type;
+	flock->l_type = file_lock.fl_type;
 	if (file_lock.fl_type != F_UNLCK)
 		posix_lock_to_flock64(flock, &file_lock);
 
-- 
2.11.0

Re: [PATCH 2/2] fs/locks: don't mess with the address limit in compat_fcntl64

[Jeff Layton]

On Mon, 2017-05-15 at 22:33 +0200, Christoph Hellwig wrote:
> Instead write a proper compat syscall that calls common helpers.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/fcntl.c | 118 +++++++++++++++++++++++++++++++++++--------------------------
>  fs/locks.c |   2 +-
>  2 files changed, 68 insertions(+), 52 deletions(-)
> 
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 671ac43c65df..9d909b029063 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -505,76 +505,92 @@ convert_fcntl_cmd(unsigned int cmd)
>  	return cmd;
>  }
>  
> +/*
> + * GETLK was successful and we need to return the data, but it needs to fit in
> + * the compat structure.
> + * l_start shouldn't be too big, unless the original start + end is greater than
> + * COMPAT_OFF_T_MAX, in which case the app was asking for trouble, so we return
> + * -EOVERFLOW in that case.  l_len could be too big, in which case we just
> + * truncate it, and only allow the app to see that part of the conflicting lock
> + * that might make sense to it anyway
> + */
> +static int fixup_compat_flock(struct flock *flock)
> +{
> +	if (flock.l_start > COMPAT_OFF_T_MAX)
> +		return -EOVERFLOW;
> +	if (flock.l_len > COMPAT_OFF_T_MAX)
> +		flock.l_len = COMPAT_OFF_T_MAX;
> +	return 0;
> +}
> +

Erm...build break above though -- flock is a pointer there, so those
should be "flock->...". I'll just squash that fix into the patch unless
you need to send a respin for other reasons.

>  COMPAT_SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
>  		       compat_ulong_t, arg)
>  {
> -	mm_segment_t old_fs;
> -	struct flock f;
> -	long ret;
> -	unsigned int conv_cmd;
> +	struct fd f = fdget_raw(fd);
> +	struct flock flock;
> +	long err = -EBADF;
> +
> +	if (!f.file)
> +		return err;
> +
> +	if (unlikely(f.file->f_mode & FMODE_PATH)) {
> +		if (!check_fcntl_cmd(cmd))
> +			goto out_put;
> +	}
> +
> +	err = security_file_fcntl(f.file, cmd, arg);
> +	if (err)
> +		goto out_put;
>  
>  	switch (cmd) {
>  	case F_GETLK:
> +		err = get_compat_flock(&flock, compat_ptr(arg));
> +		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_flock(&flock, compat_ptr(arg));
> +		break;
> +	case F_GETLK64:
> +	case F_OFD_GETLK:
> +		err = get_compat_flock64(&flock, compat_ptr(arg));
> +		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));
> +		break;
>  	case F_SETLK:
>  	case F_SETLKW:
> -		ret = get_compat_flock(&f, compat_ptr(arg));
> -		if (ret != 0)
> +		err = get_compat_flock(&flock, compat_ptr(arg));
> +		if (err)
>  			break;
> -		old_fs = get_fs();
> -		set_fs(KERNEL_DS);
> -		ret = sys_fcntl(fd, cmd, (unsigned long)&f);
> -		set_fs(old_fs);
> -		if (cmd == F_GETLK && ret == 0) {
> -			/* GETLK was successful and we need to return the data...
> -			 * but it needs to fit in the compat structure.
> -			 * l_start shouldn't be too big, unless the original
> -			 * start + end is greater than COMPAT_OFF_T_MAX, in which
> -			 * case the app was asking for trouble, so we return
> -			 * -EOVERFLOW in that case.
> -			 * l_len could be too big, in which case we just truncate it,
> -			 * and only allow the app to see that part of the conflicting
> -			 * lock that might make sense to it anyway
> -			 */
> -
> -			if (f.l_start > COMPAT_OFF_T_MAX)
> -				ret = -EOVERFLOW;
> -			if (f.l_len > COMPAT_OFF_T_MAX)
> -				f.l_len = COMPAT_OFF_T_MAX;
> -			if (ret == 0)
> -				ret = put_compat_flock(&f, compat_ptr(arg));
> -		}
> +		err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
>  		break;
> -
> -	case F_GETLK64:
>  	case F_SETLK64:
>  	case F_SETLKW64:
> -	case F_OFD_GETLK:
>  	case F_OFD_SETLK:
>  	case F_OFD_SETLKW:
> -		ret = get_compat_flock64(&f, compat_ptr(arg));
> -		if (ret != 0)
> +		err = get_compat_flock64(&flock, compat_ptr(arg));
> +		if (err)
>  			break;
> -		old_fs = get_fs();
> -		set_fs(KERNEL_DS);
> -		conv_cmd = convert_fcntl_cmd(cmd);
> -		ret = sys_fcntl(fd, conv_cmd, (unsigned long)&f);
> -		set_fs(old_fs);
> -		if ((conv_cmd == F_GETLK || conv_cmd == F_OFD_GETLK) && ret == 0) {
> -			/* need to return lock information - see above for commentary */
> -			if (f.l_start > COMPAT_LOFF_T_MAX)
> -				ret = -EOVERFLOW;
> -			if (f.l_len > COMPAT_LOFF_T_MAX)
> -				f.l_len = COMPAT_LOFF_T_MAX;
> -			if (ret == 0)
> -				ret = put_compat_flock64(&f, compat_ptr(arg));
> -		}
> +		err = fcntl_setlk(fd, f.file, convert_fcntl_cmd(cmd), &flock);
>  		break;
> -
>  	default:
> -		ret = sys_fcntl(fd, cmd, arg);
> +		err = do_fcntl(fd, cmd, arg, f.file);
>  		break;
>  	}
> -	return ret;
> +out_put:
> +	fdput(f);
> +	return err;
>  }
>  
>  COMPAT_SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd,
> diff --git a/fs/locks.c b/fs/locks.c
> index 054f6fb7641e..8b4e78e4c054 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2325,7 +2325,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
>  	if (error)
>  		goto out;
>  
> -	flock.l_type = file_lock.fl_type;
> +	flock->l_type = file_lock.fl_type;
>  	if (file_lock.fl_type != F_UNLCK)
>  		posix_lock_to_flock64(flock, &file_lock);
>  

-- 
Jeff Layton <jlayton@poochiereds.net>

Re: [PATCH 2/2] fs/locks: don't mess with the address limit in compat_fcntl64

[Christoph Hellwig]

On Tue, May 16, 2017 at 06:46:10AM -0400, Jeff Layton wrote:
> Erm...build break above though -- flock is a pointer there, so those
> should be "flock->...". I'll just squash that fix into the patch unless
> you need to send a respin for other reasons.

Thanks.  I did a last minute fixup to factor this into a helper and messed
up..

Re: rewrite file locking compat syscalls

[Jeff Layton]

On Mon, 2017-05-15 at 22:33 +0200, Christoph Hellwig wrote:
> Export proper lowlevel helper and use them from the compat code instead
> of playing set_fs games.
> 

Looks good -- nice cleanup...and yeah, ISTR that I broke ARM when
merging the OFD lock code because I screwed up the set_fs calls. So, I'm
all for this change.

Christoph, do you want me to plan to merge these for v4.13? If so, I'll
get them into my linux-next branch soon so we can start testing them.

Thanks,

Reviewed-by: Jeff Layton <jlayton@redhat.com>