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r/o bind mounts: rearrange may_open() to be r/o friendly 

may_open() calls vfs_permission() before it does checks for IS_RDONLY(inode).
It checks _again_ inside of vfs_permission().

The check inside of vfs_permission() is going away eventually.  With the
mnt_want/drop_write() functions, all of the r/o checks (except for this one)
are consistently done before calling permission().  Because of this, I'd like
to use permission() to hold a debugging check to make sure that the
mnt_want/drop_write() calls are actually being made.

So, to do this:
1. remove the IS_RDONLY() check from permission()
2. enforce that you must mnt_want_write() before
   even calling permission()
3. actually add the debugging check to permission()

We need to rearrange may_open() to do r/o checks before calling permission().
Here's the patch.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dave Hansen 2007-10-16 23:31:14 -07:00 committed by Linus Torvalds
parent ce8d2cdf3d
commit b41572e929
1 changed files with 4 additions and 4 deletions
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8
fs/namei.c
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@ -1604,10 +1604,6 @@ int may_open(struct nameidata *nd, int acc_mode, int flag)
if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE)) if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
return -EISDIR; return -EISDIR;
error = vfs_permission(nd, acc_mode);
if (error)
return error;
/* /*
* FIFO's, sockets and device files are special: they don't * FIFO's, sockets and device files are special: they don't
* actually live on the filesystem itself, and as such you * actually live on the filesystem itself, and as such you
@ -1622,6 +1618,10 @@ int may_open(struct nameidata *nd, int acc_mode, int flag)
flag &= ~O_TRUNC; flag &= ~O_TRUNC;
} else if (IS_RDONLY(inode) && (flag & FMODE_WRITE)) } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
return -EROFS; return -EROFS;
error = vfs_permission(nd, acc_mode);
if (error)
return error;
/* /*
* An append-only file must be opened in append mode for writing. * An append-only file must be opened in append mode for writing.
*/ */