linux-kernel - Re: [PATCH -v3] Only honor the FIGETBSZ ioctl for regular files and directories

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Message-ID: <4D524CBE.2020300@yahoo.se>
Date:	Wed, 09 Feb 2011 09:13:50 +0100
From:	anders franzen <anders.franzen@...oo.se>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -v3] Only honor the FIGETBSZ ioctl for regular files and
 directories

Vad happened with the patch below. It was ''signed off'' more than half 
a year ago, and it is not in any of the latest kernel yet.

I ask, because I spend a week debugging the 'dvbloopback' driver, which 
uses '2' as a private ioctl for a read command. Not easy to find.

Can a driver not have private ioctls?
Should this be fixed in the driver?, I have now RESERVED the value 2 in 
the driver. But this does not
guarantee that someone invents FIGETBSZ_V2 and assigned the value 3 to it.

Regards
   /Anders

FIGETBSZ has an ioctl number of _IO(0x00,2) == 2, which can conflict
with device driver ioctls. Let's avoid the potential for problems by
only honoring the ioctl number for files where this ioctl is likely
going to be useful: for regular files and directories

Thanks to Johannes Stezenbach for pointing this consequence of commit
19ba0559.

Signed-off-by: "Theodore Ts'o" <tytso@...xxxx>
Cc: Al Viro <viro@...xxxxxxxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@...xxxxxxxxxxxxxxx>
Cc: Johannes Stezenbach <js@...xxxxxx>
---

Fixed up commit description

fs/compat_ioctl.c | 6 +++++-
fs/ioctl.c | 5 ++++-
2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index 641640d..b8607fe 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -1715,8 +1715,12 @@ asmlinkage long compat_sys_ioctl(unsigned int fd, 
unsigned int cmd,
goto out_fput;
#endif
- case FIBMAP:
case FIGETBSZ:
+ if (S_ISDIR(filp->f_path.dentry->d_inode->i_mode))
+ break;
+ /*FALL THROUGH */
+
+ case FIBMAP:
case FIONREAD:
if (S_ISREG(filp->f_path.dentry->d_inode->i_mode))
break;
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 2d140a7..e578dab 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -597,7 +597,10 @@ int do_vfs_ioctl(struct file *filp, unsigned int 
fd, unsigned int cmd,
{
struct inode *inode = filp->f_path.dentry->d_inode;
int __user *p = (int __user *)arg;
- return put_user(inode->i_sb->s_blocksize, p);
+
+ if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
+ return put_user(inode->i_sb->s_blocksize, p);
+ /* FALL THROUGH */
}

default:
-- 
1.7.0.4

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