| Message ID | 3411f396-a41e-76cb-7836-941fbade81dc@I-love.SAKURA.ne.jp (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [(urgent)] vfs: fix uninitialized uid/gid in chown_common() | expand |
On Mon, Sep 19, 2022 at 08:05:12PM +0900, Tetsuo Handa wrote: > syzbot is reporting uninit-value in tomoyo_path_chown() [1], for > chown_common() is by error passing uninitialized newattrs.ia_vfsuid to > security_path_chown() via from_vfsuid() when user == -1 is passed. > We must initialize newattrs.ia_vfs{u,g}id fields in order to make > from_vfs{u,g}id() work. > > Link: https://syzkaller.appspot.com/bug?extid=541e21dcc32c4046cba9 [1] > Reported-by: syzbot <syzbot+541e21dcc32c4046cba9@syzkaller.appspotmail.com> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > --- Odd that we didn't get any of the reports. Thanks for relying this. I'll massage this a tiny bit, apply and will test with syzbot.
On Mon, Sep 19, 2022 at 05:12:25PM +0200, Christian Brauner wrote: > On Mon, Sep 19, 2022 at 08:05:12PM +0900, Tetsuo Handa wrote: > > syzbot is reporting uninit-value in tomoyo_path_chown() [1], for > > chown_common() is by error passing uninitialized newattrs.ia_vfsuid to > > security_path_chown() via from_vfsuid() when user == -1 is passed. > > We must initialize newattrs.ia_vfs{u,g}id fields in order to make > > from_vfs{u,g}id() work. > > > > Link: https://syzkaller.appspot.com/bug?extid=541e21dcc32c4046cba9 [1] > > Reported-by: syzbot <syzbot+541e21dcc32c4046cba9@syzkaller.appspotmail.com> > > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > > --- > > Odd that we didn't get any of the reports. Thanks for relying this. > I'll massage this a tiny bit, apply and will test with syzbot. Fyi, Seth.
On Mon, Sep 19, 2022 at 05:14:14PM +0200, Christian Brauner wrote: > On Mon, Sep 19, 2022 at 05:12:25PM +0200, Christian Brauner wrote: > > On Mon, Sep 19, 2022 at 08:05:12PM +0900, Tetsuo Handa wrote: > > > syzbot is reporting uninit-value in tomoyo_path_chown() [1], for > > > chown_common() is by error passing uninitialized newattrs.ia_vfsuid to > > > security_path_chown() via from_vfsuid() when user == -1 is passed. > > > We must initialize newattrs.ia_vfs{u,g}id fields in order to make > > > from_vfs{u,g}id() work. > > > > > > Link: https://syzkaller.appspot.com/bug?extid=541e21dcc32c4046cba9 [1] > > > Reported-by: syzbot <syzbot+541e21dcc32c4046cba9@syzkaller.appspotmail.com> > > > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > > > --- > > > > Odd that we didn't get any of the reports. Thanks for relying this. > > I'll massage this a tiny bit, apply and will test with syzbot. > > Fyi, Seth. Because the modules are ignoring ia_valid & ATTR_XID?
On Mon, Sep 19, 2022 at 06:41:02PM -0500, Serge E. Hallyn wrote: > On Mon, Sep 19, 2022 at 05:14:14PM +0200, Christian Brauner wrote: > > On Mon, Sep 19, 2022 at 05:12:25PM +0200, Christian Brauner wrote: > > > On Mon, Sep 19, 2022 at 08:05:12PM +0900, Tetsuo Handa wrote: > > > > syzbot is reporting uninit-value in tomoyo_path_chown() [1], for > > > > chown_common() is by error passing uninitialized newattrs.ia_vfsuid to > > > > security_path_chown() via from_vfsuid() when user == -1 is passed. > > > > We must initialize newattrs.ia_vfs{u,g}id fields in order to make > > > > from_vfs{u,g}id() work. > > > > > > > > Link: https://syzkaller.appspot.com/bug?extid=541e21dcc32c4046cba9 [1] > > > > Reported-by: syzbot <syzbot+541e21dcc32c4046cba9@syzkaller.appspotmail.com> > > > > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > > > > --- > > > > > > Odd that we didn't get any of the reports. Thanks for relying this. > > > I'll massage this a tiny bit, apply and will test with syzbot. > > > > Fyi, Seth. > > Because the modules are ignoring ia_valid & ATTR_XID? security_path_chown() takes ids as arguments, not struct iattr. int security_path_chown(const struct path *path, kuid_t uid, kgid_t gid) The ones being passed are now taken from iattr and thus potentially not initialized. Even if we change it to only call security_path_chown() when one of ATTR_{U,G}ID is set the other might not be set, so initializing iattr.ia_vfs{u,g}id makes sense to me and should match the old behavior of passing invalid ids in this situation. What I don't understand is why security_path_chown() is even necessary when we also have security_inode_setattr(), which also gets called during chown and gets the full iattr struct. Maybe there's a good reason, but at first glance it seems like it could do any checks that security_path_chown() is doing. Seth
On Mon, Sep 19, 2022 at 07:25:39PM -0500, Seth Forshee wrote: > On Mon, Sep 19, 2022 at 06:41:02PM -0500, Serge E. Hallyn wrote: > > On Mon, Sep 19, 2022 at 05:14:14PM +0200, Christian Brauner wrote: > > > On Mon, Sep 19, 2022 at 05:12:25PM +0200, Christian Brauner wrote: > > > > On Mon, Sep 19, 2022 at 08:05:12PM +0900, Tetsuo Handa wrote: > > > > > syzbot is reporting uninit-value in tomoyo_path_chown() [1], for > > > > > chown_common() is by error passing uninitialized newattrs.ia_vfsuid to > > > > > security_path_chown() via from_vfsuid() when user == -1 is passed. > > > > > We must initialize newattrs.ia_vfs{u,g}id fields in order to make > > > > > from_vfs{u,g}id() work. > > > > > > > > > > Link: https://syzkaller.appspot.com/bug?extid=541e21dcc32c4046cba9 [1] > > > > > Reported-by: syzbot <syzbot+541e21dcc32c4046cba9@syzkaller.appspotmail.com> > > > > > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > > > > > --- > > > > > > > > Odd that we didn't get any of the reports. Thanks for relying this. > > > > I'll massage this a tiny bit, apply and will test with syzbot. > > > > > > Fyi, Seth. > > > > Because the modules are ignoring ia_valid & ATTR_XID? > > security_path_chown() takes ids as arguments, not struct iattr. > > int security_path_chown(const struct path *path, kuid_t uid, kgid_t gid) > > The ones being passed are now taken from iattr and thus potentially not > initialized. Even if we change it to only call security_path_chown() > when one of ATTR_{U,G}ID is set the other might not be set, so > initializing iattr.ia_vfs{u,g}id makes sense to me and should match the > old behavior of passing invalid ids in this situation. > > What I don't understand is why security_path_chown() is even necessary > when we also have security_inode_setattr(), which also gets called > during chown and gets the full iattr struct. Maybe there's a good > reason, but at first glance it seems like it could do any checks that > security_path_chown() is doing. Maybe the important difference is that one takes the path as an argument and the other only takes the dentry? I guess that might be it, though it still feels kind of redundant.
On 2022/09/20 9:29, Seth Forshee wrote: >>>>> Odd that we didn't get any of the reports. Thanks for relying this. >>>>> I'll massage this a tiny bit, apply and will test with syzbot. Since KMSAN is not yet upstreamed, uninit-value reports can come only after bugs reached upstream kernels. Also, only LSMs which implement security_path_chown() hook and checks uid/gid values (i.e. TOMOYO) would catch this bug. >>>> >>>> Fyi, Seth. >>> >>> Because the modules are ignoring ia_valid & ATTR_XID? >> >> security_path_chown() takes ids as arguments, not struct iattr. >> >> int security_path_chown(const struct path *path, kuid_t uid, kgid_t gid) >> >> The ones being passed are now taken from iattr and thus potentially not >> initialized. Even if we change it to only call security_path_chown() >> when one of ATTR_{U,G}ID is set the other might not be set, so >> initializing iattr.ia_vfs{u,g}id makes sense to me and should match the >> old behavior of passing invalid ids in this situation. >> >> What I don't understand is why security_path_chown() is even necessary >> when we also have security_inode_setattr(), which also gets called >> during chown and gets the full iattr struct. Maybe there's a good >> reason, but at first glance it seems like it could do any checks that >> security_path_chown() is doing. > > Maybe the important difference is that one takes the path as an argument > and the other only takes the dentry? I guess that might be it, though it > still feels kind of redundant. security_path_*() hooks are used by LSMs which check absolute pathnames. Thus, these hooks are not redundant.
diff --git a/fs/open.c b/fs/open.c index 8a813fa5ca56..0550efb7b53a 100644 --- a/fs/open.c +++ b/fs/open.c @@ -709,6 +709,8 @@ int chown_common(const struct path *path, uid_t user, gid_t group) kuid_t uid; kgid_t gid; + newattrs.ia_vfsuid = VFSUIDT_INIT(KUIDT_INIT(-1)); + newattrs.ia_vfsgid = VFSGIDT_INIT(KGIDT_INIT(-1)); uid = make_kuid(current_user_ns(), user); gid = make_kgid(current_user_ns(), group);
syzbot is reporting uninit-value in tomoyo_path_chown() [1], for chown_common() is by error passing uninitialized newattrs.ia_vfsuid to security_path_chown() via from_vfsuid() when user == -1 is passed. We must initialize newattrs.ia_vfs{u,g}id fields in order to make from_vfs{u,g}id() work. Link: https://syzkaller.appspot.com/bug?extid=541e21dcc32c4046cba9 [1] Reported-by: syzbot <syzbot+541e21dcc32c4046cba9@syzkaller.appspotmail.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> --- fs/open.c | 2 ++ 1 file changed, 2 insertions(+)