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compat_ioctl: fix FIONREAD on devices

Message ID 20200207170447.1251404-1-arnd@arndb.de (mailing list archive)
State New, archived
Headers show
Series compat_ioctl: fix FIONREAD on devices | expand

Commit Message

Arnd Bergmann Feb. 7, 2020, 5:04 p.m. UTC
My final cleanup patch for sys_compat_ioctl() introduced a regression on
the FIONREAD ioctl command, which is used for both regular and special
files, but only works on regular files after my patch, as I had missed
the warning that Al Viro put into a comment right above it.

Change it back so it can work on any file again by moving the implementation
to do_vfs_ioctl() instead.

Fixes: 77b9040195de ("compat_ioctl: simplify the implementation")
Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Reported-by: youling257 <youling257@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Untested so far. Christian and youling257, can you see if this patch
addresses your problems?
 fs/ioctl.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)
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diff --git a/fs/ioctl.c b/fs/ioctl.c
index 7c9a5df5a597..5152c98cfc30 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -523,13 +523,9 @@  static int compat_ioctl_preallocate(struct file *file, int mode,
 static int file_ioctl(struct file *filp, unsigned int cmd, int __user *p)
-	struct inode *inode = file_inode(filp);
 	switch (cmd) {
 	case FIBMAP:
 		return ioctl_fibmap(filp, p);
-	case FIONREAD:
-		return put_user(i_size_read(inode) - filp->f_pos, p);
 	case FS_IOC_RESVSP64:
 		return ioctl_preallocate(filp, 0, p);
@@ -721,6 +717,13 @@  static int do_vfs_ioctl(struct file *filp, unsigned int fd,
 		return ioctl_file_dedupe_range(filp, argp);
+	case FIONREAD:
+		if (!S_ISREG(inode->i_mode))
+			return vfs_ioctl(filp, cmd, arg);
+		return put_user(i_size_read(inode) - filp->f_pos,
+				(int __user *)argp);
 		if (S_ISREG(inode->i_mode))
 			return file_ioctl(filp, cmd, argp);