Messages in this thread Patch in this message | | | Subject | [PATCH 02/24] rearrange may_open() to be r/o friendly | From | Dave Hansen <> | Date | Mon, 17 Sep 2007 11:27:20 -0700 |
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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. enable a debugging in permission()
We need to rearrange may_open(). Here's the patch.
Signed-off-by: Dave Hansen <haveblue@us.ibm.com> ---
lxc-dave/fs/namei.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
diff -puN fs/namei.c~rearrange-permission-and-ro-checks-in-may_open fs/namei.c --- lxc/fs/namei.c~rearrange-permission-and-ro-checks-in-may_open 2007-09-17 09:43:56.000000000 -0700 +++ lxc-dave/fs/namei.c 2007-09-17 09:43:56.000000000 -0700 @@ -228,6 +228,10 @@ int generic_permission(struct inode *ino int permission(struct inode *inode, int mask, struct nameidata *nd) { int retval, submask; + struct vfsmount *mnt = NULL; + + if (nd) + mnt = nd->mnt; if (mask & MAY_WRITE) { umode_t mode = inode->i_mode; @@ -251,7 +255,7 @@ int permission(struct inode *inode, int * MAY_EXEC on regular files is denied if the fs is mounted * with the "noexec" flag. */ - if (nd && nd->mnt && (nd->mnt->mnt_flags & MNT_NOEXEC)) + if (mnt && (mnt->mnt_flags & MNT_NOEXEC)) return -EACCES; } @@ -1604,10 +1608,6 @@ int may_open(struct nameidata *nd, int a if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE)) return -EISDIR; - error = vfs_permission(nd, acc_mode); - if (error) - return error; - /* * FIFO's, sockets and device files are special: they don't * actually live on the filesystem itself, and as such you @@ -1622,6 +1622,10 @@ int may_open(struct nameidata *nd, int a flag &= ~O_TRUNC; } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE)) return -EROFS; + + error = vfs_permission(nd, acc_mode); + if (error) + return error; /* * An append-only file must be opened in append mode for writing. */ _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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