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SubjectRe: [NFS] [PATCH 1/3] VFS: make notify_change pass ATTR_KILL_S*ID to setattr operations
Jeff Layton wrote:
> Make notify_change not clear the ATTR_KILL_S*ID bits in the ia_vaid that
> gets passed to the setattr inode operation. This allows the filesystems
> to reinterpret whether this mode change is simply intended to clear the
> setuid/setgid bits.
>
> This means that notify_change should never be called with both ATTR_MODE
> and either of the ATTR_KILL_S*ID bits set, since the filesystem would
> have no way to know what part of the mode change was intentional. If
> it is called this way, consider it a BUG().
>
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
> fs/attr.c | 22 ++++++++++++----------
> 1 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/fs/attr.c b/fs/attr.c
> index ae58bd3..f98d10c 100644
> --- a/fs/attr.c
> +++ b/fs/attr.c
> @@ -103,12 +103,11 @@ EXPORT_SYMBOL(inode_setattr);
> int notify_change(struct dentry * dentry, struct iattr * attr)
> {
> struct inode *inode = dentry->d_inode;
> - mode_t mode;
> + mode_t mode = inode->i_mode;
> int error;
> struct timespec now;
> unsigned int ia_valid = attr->ia_valid;
>
> - mode = inode->i_mode;
> now = current_fs_time(inode->i_sb);
>
> attr->ia_ctime = now;
> @@ -125,18 +124,21 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
> if (error)
> return error;
> }
> +
> + /*
> + * It's not valid to pass an iattr with both ATTR_MODE and
> + * ATTR_KILL_S*ID set.
> + */
> + if (ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID) && ia_valid & ATTR_MODE)
>

If you would, please add some parentheses to show and make
explicit what the bindings are. This is:

if ((ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) &&
(ia_valid & ATTR_MODE))

Thanx...

ps

> + BUG();
> +
> if (ia_valid & ATTR_KILL_SUID) {
> - attr->ia_valid &= ~ATTR_KILL_SUID;
> if (mode & S_ISUID) {
> - if (!(ia_valid & ATTR_MODE)) {
> - ia_valid = attr->ia_valid |= ATTR_MODE;
> - attr->ia_mode = inode->i_mode;
> - }
> - attr->ia_mode &= ~S_ISUID;
> + ia_valid = attr->ia_valid |= ATTR_MODE;
> + attr->ia_mode = (inode->i_mode & ~S_ISUID);
> }
> }
> if (ia_valid & ATTR_KILL_SGID) {
> - attr->ia_valid &= ~ ATTR_KILL_SGID;
> if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
> if (!(ia_valid & ATTR_MODE)) {
> ia_valid = attr->ia_valid |= ATTR_MODE;
> @@ -145,7 +147,7 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
> attr->ia_mode &= ~S_ISGID;
> }
> }
> - if (!attr->ia_valid)
> + if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
> return 0;
>
> if (ia_valid & ATTR_SIZE)
>

-
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