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Date: Thu, 11 Jun 2020 04:41:02 +0000 From: Sargun Dhillon <sargun@...gun.me> To: Kees Cook <keescook@...omium.org> Cc: Christian Brauner <christian.brauner@...ntu.com>, containers@...ts.linux-foundation.org, Giuseppe Scrivano <gscrivan@...hat.com>, Robert Sesek <rsesek@...gle.com>, Chris Palmer <palmer@...gle.com>, Jann Horn <jannh@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Daniel Wagner <daniel.wagner@...-carit.de>, linux-kernel@...r.kernel.org, Matt Denton <mpdenton@...gle.com>, John Fastabend <john.r.fastabend@...el.com>, linux-fsdevel@...r.kernel.org, Tejun Heo <tj@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, cgroups@...r.kernel.org, stable@...r.kernel.org, "David S . Miller" <davem@...emloft.net> Subject: Re: [PATCH v3 1/4] fs, net: Standardize on file_receive helper to move fds across processes On Wed, Jun 10, 2020 at 07:59:55PM -0700, Kees Cook wrote: > > Yeah, that seems reasonable. Here's the diff for that part: > > diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h > index 7b6028b399d8..98bf19b4e086 100644 > --- a/include/uapi/linux/seccomp.h > +++ b/include/uapi/linux/seccomp.h > @@ -118,7 +118,6 @@ struct seccomp_notif_resp { > > /** > * struct seccomp_notif_addfd > - * @size: The size of the seccomp_notif_addfd datastructure > * @id: The ID of the seccomp notification > * @flags: SECCOMP_ADDFD_FLAG_* > * @srcfd: The local fd number > @@ -126,7 +125,6 @@ struct seccomp_notif_resp { > * @newfd_flags: The O_* flags the remote FD should have applied > */ > struct seccomp_notif_addfd { > - __u64 size; > __u64 id; > __u32 flags; > __u32 srcfd; > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > index 3c913f3b8451..00cbdad6c480 100644 > --- a/kernel/seccomp.c > +++ b/kernel/seccomp.c > @@ -1297,14 +1297,9 @@ static long seccomp_notify_addfd(struct seccomp_filter *filter, > struct seccomp_notif_addfd addfd; > struct seccomp_knotif *knotif; > struct seccomp_kaddfd kaddfd; > - u64 size; > int ret; > > - ret = get_user(size, &uaddfd->size); > - if (ret) > - return ret; > - > - ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size); > + ret = copy_from_user(&addfd, uaddfd, sizeof(addfd)); > if (ret) > return ret; > > Looks good to me. If we ever change the size of this struct, we can do the work then to copy_struct_from_user. > > > > ---- > > +#define SECCOMP_IOCTL_NOTIF_ADDFD SECCOMP_IOR(3, \ > > + struct seccomp_notif_addfd) > > > > Lastly, what I believe to be a small mistake, it should be SECCOMP_IOW, based on > > the documentation in ioctl.h -- "_IOW means userland is writing and kernel is > > reading." > > Oooooh. Yeah; good catch. Uhm, that means SECCOMP_IOCTL_NOTIF_ID_VALID > is wrong too, yes? Tycho, Christian, how disruptive would this be to > fix? (Perhaps support both and deprecate the IOR version at some point > in the future?) I think at a minimum we should change the uapi, and accept both (for now). Maybe a pr_warn_once telling people not to use the old one. I can do the patch, if you want. > > Diff for just addfd's change: > > diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h > index 7b6028b399d8..98bf19b4e086 100644 > --- a/include/uapi/linux/seccomp.h > +++ b/include/uapi/linux/seccomp.h > @@ -146,7 +144,7 @@ struct seccomp_notif_addfd { > struct seccomp_notif_resp) > #define SECCOMP_IOCTL_NOTIF_ID_VALID SECCOMP_IOR(2, __u64) > /* On success, the return value is the remote process's added fd number */ > -#define SECCOMP_IOCTL_NOTIF_ADDFD SECCOMP_IOR(3, \ > +#define SECCOMP_IOCTL_NOTIF_ADDFD SECCOMP_IOW(3, \ > struct seccomp_notif_addfd) > > #endif /* _UAPI_LINUX_SECCOMP_H */ > > -- > Kees Cook Looks good. Thank you.
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