Date: Tue, 30 Apr 2024 12:09:02 +0200
From: Jan Kara <jack@...e.cz>
To: cgzones@...glemail.com
Cc: x86@...nel.org, linux-alpha@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-ia64@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
	linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, audit@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
	Richard Henderson <richard.henderson@...aro.org>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Matt Turner <mattst88@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Michal Simek <monstr@...str.eu>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
	Helge Deller <deller@....de>, Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Rich Felker <dalias@...c.org>,
	John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
	"David S. Miller" <davem@...emloft.net>,
	Andreas Larsson <andreas@...sler.com>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Chris Zankel <chris@...kel.net>,
	Max Filippov <jcmvbkbc@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Paul Moore <paul@...l-moore.com>, Eric Paris <eparis@...hat.com>,
	Arnd Bergmann <arnd@...db.de>, Jens Axboe <axboe@...nel.dk>,
	Pavel Begunkov <asml.silence@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Palmer Dabbelt <palmer@...ive.com>,
	Miklos Szeredi <mszeredi@...hat.com>, Nhat Pham <nphamcs@...il.com>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Kees Cook <keescook@...omium.org>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Mark Rutland <mark.rutland@....com>, io-uring@...r.kernel.org
Subject: Re: [PATCH v3 2/2] fs/xattr: add *at family syscalls

On Fri 26-04-24 18:20:14, Christian Göttsche wrote:
> From: Christian Göttsche <cgzones@...glemail.com>
> 
> Add the four syscalls setxattrat(), getxattrat(), listxattrat() and
> removexattrat().  Those can be used to operate on extended attributes,
> especially security related ones, either relative to a pinned directory
> or on a file descriptor without read access, avoiding a
> /proc/<pid>/fd/<fd> detour, requiring a mounted procfs.
> 
> One use case will be setfiles(8) setting SELinux file contexts
> ("security.selinux") without race conditions and without a file
> descriptor opened with read access requiring SELinux read permission.
> 
> Use the do_{name}at() pattern from fs/open.c.
> 
> Pass the value of the extended attribute, its length, and for
> setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added
> struct xattr_args to not exceed six syscall arguments and not
> merging the AT_* and XATTR_* flags.
> 
> Signed-off-by: Christian Göttsche <cgzones@...glemail.com>

The patch looks good to me. Just a few nits below:

> -static int path_setxattr(const char __user *pathname,
> +static int do_setxattrat(int dfd, const char __user *pathname, unsigned int at_flags,

Can we please stay within 80 columns (happens in multiple places in the
patch)? I don't insist but it makes things easier to read in some setups so
I prefer it.

> @@ -852,13 +908,21 @@ listxattr(struct dentry *d, char __user *list, size_t size)
>  	return error;
>  }
>  
> -static ssize_t path_listxattr(const char __user *pathname, char __user *list,
> -			      size_t size, unsigned int lookup_flags)
> +static ssize_t do_listxattrat(int dfd, const char __user *pathname, char __user *list,
> +			      size_t size, int flags)

So I like how in previous syscalls you have 'at_flags', 'lookup_flags', and
'xattr_flags'. That makes things much easier to digest. Can you please stay
with that convention here as well and call this argument 'at_flags'? Also I
think the argument ordering like "dfd, pathname, at_flags, list, size" is
more consistent with other syscalls you define.

> @@ -870,16 +934,22 @@ static ssize_t path_listxattr(const char __user *pathname, char __user *list,
>  	return error;
>  }
>  
> +SYSCALL_DEFINE5(listxattrat, int, dfd, const char __user *, pathname, char __user *, list,
> +		size_t, size, int, flags)
> +{
> +	return do_listxattrat(dfd, pathname, list, size, flags);
> +}
> +

Same comment as above - "flags" -> "at_flags" and reorder args please.

> @@ -917,13 +987,21 @@ removexattr(struct mnt_idmap *idmap, struct dentry *d,
>  	return vfs_removexattr(idmap, d, kname);
>  }
>  
> -static int path_removexattr(const char __user *pathname,
> -			    const char __user *name, unsigned int lookup_flags)
> +static int do_removexattrat(int dfd, const char __user *pathname,
> +			    const char __user *name, int flags)
>  {

Same comment as above - "flags" -> "at_flags" and reorder args please.

> @@ -939,16 +1017,22 @@ static int path_removexattr(const char __user *pathname,
>  	return error;
>  }
>  
> +SYSCALL_DEFINE4(removexattrat, int, dfd, const char __user *, pathname,
> +		const char __user *, name, int, flags)
> +{

Same comment as above - "flags" -> "at_flags" and reorder args please.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

Powered by blists - more mailing lists