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Message-ID: <a70e8b062fc422e351fe2369b9979a623fa05dfa.camel@xry111.site>
Subject: Re: [PATCH] LoongArch: Define __ARCH_WANT_NEW_STAT in unistd.h
From: Xi Ruoyao <xry111@xry111.site>
To: Arnd Bergmann <arnd@arndb.de>, Huacai Chen <chenhuacai@kernel.org>
Cc: Huacai Chen <chenhuacai@loongson.cn>, loongarch@lists.linux.dev,
 Linux-Arch <linux-arch@vger.kernel.org>, Xuefeng Li
 <lixuefeng@loongson.cn>, guoren <guoren@kernel.org>, WANG Xuerui
 <kernel@xen0n.name>, Jiaxun Yang <jiaxun.yang@flygoat.com>,
 linux-kernel@vger.kernel.org,  loongson-kernel@lists.loongnix.cn,
 stable@vger.kernel.org
Date: Sat, 15 Jun 2024 21:12:26 +0800
In-Reply-To: <08ff168afc09fd108ec489a3c9360d4e704fa7dc.camel@xry111.site>
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On Sat, 2024-06-15 at 20:12 +0800, Xi Ruoyao wrote:
> On Sat, 2024-06-15 at 13:47 +0200, Arnd Bergmann wrote:
>=20
> /* snip */
>=20
> > > > > We can only wait for the seccomp side to be fixed now? Or we can =
get
> > > > > this patch upstream for LoongArch64 at the moment, and wait for
> > > > > seccomp to fix RISCV32 (and LoongArch32) in future?
> > > >=20
> > > > I'm wondering why not just introduce a new syscall or extend statx =
with
> > > > a new flag, as we've discussed many times.=C2=A0 They have their ow=
n
> > > > disadvantages but better than this, IMO.
> > > We should move things forward, in any way. :)
> >=20
> > Wouldn't it be sufficient to move the AT_EMPTY_PATH hack
> > from vfs_fstatat() to vfs_statx() so we can make them
> > behave the same way?
> >=20
> > As far as I can tell, the only difference between the two is
> > that fstatat64() and similar already has added the check for
> > zero-length strings in order to make using vfs_fstatat()
> > fast and safe when called from glibc stat().
>=20
> Do you mean https://git.kernel.org/torvalds/c/9013c51c630a?=C2=A0 It (onl=
y
> partially) fix the performance issue but it won't help seccomp.=C2=A0 The
> problem is you cannot check if the string is zero-length with seccomp.
> Thus seccomp cannot audit fstatat properly as well.
>=20
> In [Firefox] *all* fstatat (and statx) calls are trapped and *the signal
> handler* audit this fstatat call.=C2=A0 If flags & AT_EMPTY_PATH and path=
 is
> zero-length, it calls fstat to do the job.=C2=A0 But on LoongArch there i=
s no
> way to "do the job" as the only stat-family call is statx.
>=20
> [Firefox]:https://searchfox.org/mozilla-central/source/security/sandbox/l=
inux/SandboxFilter.cpp#364

Just spent some brain cycles to make a quick hack adding a new statx
flag.  Patch attached.

--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University

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