On Wed, Oct 16, 2024 at 03:23:39PM +0200, Jan Kara wrote: > On Wed 16-10-24 14:37:19, Alessandro Zanni wrote: > > Fix uninitialized value issue in from_kuid by initializing the newattrs > > structure in do_truncate() method. > > Thanks for the fix. It would be helpful to provide a bit more information > in the changelog so that one doesn't have to open the referenced syzbot > report to understand the problem. In this case I'd write something like: > > ocfs2_setattr() uses attr->ia_uid in a trace point even though ATTR_UID > isn't set. Initialize all fields of newattrs to avoid uninitialized > variable use. > > But see below as I don't think this is really the right fix. Agreed. > > > Fixes: uninit-value in from_kuid reported here > > https://syzkaller.appspot.com/bug?extid=6c55f725d1bdc8c52058 > > Fixes tag should reference some preexisting commit this patch is fixing. As > such this tag is not really applicable here. Keeping the syzbot reference > in Reported-by and Closes (or possibly change that to References) is good > enough. > > > Reported-by: syzbot+6c55f725d1bdc8c52058@xxxxxxxxxxxxxxxxxxxxxxxxx > > Closes: https://syzkaller.appspot.com/bug?extid=6c55f725d1bdc8c52058 > > Signed-off-by: Alessandro Zanni <alessandro.zanni87@xxxxxxxxx> > > --- > > fs/open.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/open.c b/fs/open.c > > index acaeb3e25c88..57c298b1db2c 100644 > > --- a/fs/open.c > > +++ b/fs/open.c > > @@ -40,7 +40,7 @@ int do_truncate(struct mnt_idmap *idmap, struct dentry *dentry, > > loff_t length, unsigned int time_attrs, struct file *filp) > > { > > int ret; > > - struct iattr newattrs; > > + struct iattr newattrs = {0}; > > We usually perform such initialization as: > struct iattr newattrs = {}; > > That being said there are many more places calling notify_change() and none > of them is doing the initialization so this patch only fixes that one > particular syzbot reproducer but doesn't really deal with the problem. > Looking at the bigger picture I think the right solution really is to fix > ocfs2_setattr() to not touch attr->ia_uid when ATTR_UID isn't set and > similarly for attr->ia_gid and ATTR_GID. Yes, that's what we did for similar bugs.
