| Message ID | 1491555701-16608-4-git-send-email-amir73il@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Apr 7, 2017 at 11:01 AM, Amir Goldstein <amir73il@gmail.com> wrote: > For overlay file open, check IS_APPEND() on the real upper inode > inside d_real(), because the overlay inode does not have the > S_APPEND flag and IS_APPEND() can only be checked at open time. > > Note that because overlayfs does not copy up the chattr inode flags > (i.e. S_APPEND, S_IMMUTABLE), the IS_APPEND() check is only relevant > for upper inodes that were set with chattr +a and not to lower > inodes that had chattr +a before copy up. Okay. Maybe rename ovl_may_open() to ovl_check_append_only(), because that what it does. Thanks, Miklos > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > --- > fs/overlayfs/super.c | 30 +++++++++++++++++++++++++++--- > 1 file changed, 27 insertions(+), 3 deletions(-) > > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c > index c9e70d3..13806b8 100644 > --- a/fs/overlayfs/super.c > +++ b/fs/overlayfs/super.c > @@ -49,11 +49,30 @@ static void ovl_dentry_release(struct dentry *dentry) > } > } > > +static int ovl_may_open(struct dentry *dentry, int flag) > +{ > + struct inode *inode = dentry->d_inode; > + > + /* > + * This test was moot in vfs may_open() because overlay inode does > + * not have the S_APPEND flag > + */ > + if (IS_APPEND(inode)) { > + if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) > + return -EPERM; > + if (flag & O_TRUNC) > + return -EPERM; > + } > + > + return 0; > +} > + > static struct dentry *ovl_d_real(struct dentry *dentry, > const struct inode *inode, > unsigned int open_flags) > { > struct dentry *real; > + int err; > > if (!d_is_reg(dentry)) { > if (!inode || inode == d_inode(dentry)) > @@ -65,15 +84,20 @@ static struct dentry *ovl_d_real(struct dentry *dentry, > return dentry; > > if (open_flags) { > - int err = ovl_open_maybe_copy_up(dentry, open_flags); > - > + err = ovl_open_maybe_copy_up(dentry, open_flags); > if (err) > return ERR_PTR(err); > } > > real = ovl_dentry_upper(dentry); > - if (real && (!inode || inode == d_inode(real))) > + if (real && (!inode || inode == d_inode(real))) { > + if (!inode) { > + err = ovl_may_open(real, open_flags); > + if (err) > + return ERR_PTR(err); > + } > return real; > + } > > real = ovl_dentry_lower(dentry); > if (!real) > -- > 2.7.4 >
On Fri, Apr 7, 2017 at 4:33 PM, Miklos Szeredi <miklos@szeredi.hu> wrote: > On Fri, Apr 7, 2017 at 11:01 AM, Amir Goldstein <amir73il@gmail.com> wrote: >> For overlay file open, check IS_APPEND() on the real upper inode >> inside d_real(), because the overlay inode does not have the >> S_APPEND flag and IS_APPEND() can only be checked at open time. >> >> Note that because overlayfs does not copy up the chattr inode flags >> (i.e. S_APPEND, S_IMMUTABLE), the IS_APPEND() check is only relevant >> for upper inodes that were set with chattr +a and not to lower >> inodes that had chattr +a before copy up. > > Okay. Maybe rename ovl_may_open() to ovl_check_append_only(), > because that what it does. Agree. Also I can pass the inode instead of dentry. > > Thanks, > Miklos > >> >> Signed-off-by: Amir Goldstein <amir73il@gmail.com> >> --- >> fs/overlayfs/super.c | 30 +++++++++++++++++++++++++++--- >> 1 file changed, 27 insertions(+), 3 deletions(-) >> >> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c >> index c9e70d3..13806b8 100644 >> --- a/fs/overlayfs/super.c >> +++ b/fs/overlayfs/super.c >> @@ -49,11 +49,30 @@ static void ovl_dentry_release(struct dentry *dentry) >> } >> } >> >> +static int ovl_may_open(struct dentry *dentry, int flag) >> +{ >> + struct inode *inode = dentry->d_inode; >> + >> + /* >> + * This test was moot in vfs may_open() because overlay inode does >> + * not have the S_APPEND flag >> + */ >> + if (IS_APPEND(inode)) { >> + if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) >> + return -EPERM; >> + if (flag & O_TRUNC) >> + return -EPERM; >> + } >> + >> + return 0; >> +} >> + >> static struct dentry *ovl_d_real(struct dentry *dentry, >> const struct inode *inode, >> unsigned int open_flags) >> { >> struct dentry *real; >> + int err; >> >> if (!d_is_reg(dentry)) { >> if (!inode || inode == d_inode(dentry)) >> @@ -65,15 +84,20 @@ static struct dentry *ovl_d_real(struct dentry *dentry, >> return dentry; >> >> if (open_flags) { >> - int err = ovl_open_maybe_copy_up(dentry, open_flags); >> - >> + err = ovl_open_maybe_copy_up(dentry, open_flags); >> if (err) >> return ERR_PTR(err); >> } >> >> real = ovl_dentry_upper(dentry); >> - if (real && (!inode || inode == d_inode(real))) >> + if (real && (!inode || inode == d_inode(real))) { >> + if (!inode) { >> + err = ovl_may_open(real, open_flags); >> + if (err) >> + return ERR_PTR(err); >> + } >> return real; >> + } >> >> real = ovl_dentry_lower(dentry); >> if (!real) >> -- >> 2.7.4 >>
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index c9e70d3..13806b8 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -49,11 +49,30 @@ static void ovl_dentry_release(struct dentry *dentry) } } +static int ovl_may_open(struct dentry *dentry, int flag) +{ + struct inode *inode = dentry->d_inode; + + /* + * This test was moot in vfs may_open() because overlay inode does + * not have the S_APPEND flag + */ + if (IS_APPEND(inode)) { + if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) + return -EPERM; + if (flag & O_TRUNC) + return -EPERM; + } + + return 0; +} + static struct dentry *ovl_d_real(struct dentry *dentry, const struct inode *inode, unsigned int open_flags) { struct dentry *real; + int err; if (!d_is_reg(dentry)) { if (!inode || inode == d_inode(dentry)) @@ -65,15 +84,20 @@ static struct dentry *ovl_d_real(struct dentry *dentry, return dentry; if (open_flags) { - int err = ovl_open_maybe_copy_up(dentry, open_flags); - + err = ovl_open_maybe_copy_up(dentry, open_flags); if (err) return ERR_PTR(err); } real = ovl_dentry_upper(dentry); - if (real && (!inode || inode == d_inode(real))) + if (real && (!inode || inode == d_inode(real))) { + if (!inode) { + err = ovl_may_open(real, open_flags); + if (err) + return ERR_PTR(err); + } return real; + } real = ovl_dentry_lower(dentry); if (!real)
For overlay file open, check IS_APPEND() on the real upper inode inside d_real(), because the overlay inode does not have the S_APPEND flag and IS_APPEND() can only be checked at open time. Note that because overlayfs does not copy up the chattr inode flags (i.e. S_APPEND, S_IMMUTABLE), the IS_APPEND() check is only relevant for upper inodes that were set with chattr +a and not to lower inodes that had chattr +a before copy up. Signed-off-by: Amir Goldstein <amir73il@gmail.com> --- fs/overlayfs/super.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-)