linux-kernel - Re: [PATCH -next] lsm: fix default return value for inode

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Message-ID: <CAHC9VhTCFOCE0E-en3HnNkPVRumzWRPcrJMF-=dxke53dOv1Gg@mail.gmail.com>
Date: Wed, 1 May 2024 12:02:25 -0400
From: Paul Moore <paul@...l-moore.com>
To: felix <fuzhen5@...wei.com>, linux-security-module@...r.kernel.org
Cc: casey@...aufler-ca.com, roberto.sassu@...wei.com, stefanb@...ux.ibm.com, 
	zohar@...ux.ibm.com, kamrankhadijadj@...il.com, andrii@...nel.org, 
	omosnace@...hat.com, linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	xiujianfeng@...wei.com, wangweiyang2@...wei.com
Subject: Re: [PATCH -next] lsm: fix default return value for inode_set(remove)xattr

On Mon, Apr 29, 2024 at 7:47 AM felix <fuzhen5@...wei.com> wrote:
>
> From: Felix Fu <fuzhen5@...wei.com>
>
> The return value of security_inode_set(remove)xattr should
> be 1. If it return 0, cap_inode_setxattr would not be
> executed when no lsm exist, which is not what we expected,
> any user could set some security.* xattr for a file.
>
> Before commit 260017f31a8c ("lsm: use default hook return
> value in call_int_hook()") was approved, this issue would
> still happened when lsm only include bpf, because bpf_lsm_
> inode_setxattr return 0 by default which cause cap_inode_set
> xattr to be not executed.
>
> Fixes: 260017f31a8c ("lsm: use default hook return value in call_int_hook()")
> Signed-off-by: Felix Fu <fuzhen5@...wei.com>
> ---
>  include/linux/lsm_hook_defs.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Adding the LSM list as that is the important list for this patch.  I'm
also just realizing we don't include lsm_hook_defs.h in the LSM
MAINTAINERS entry, I'll submit a patch for that shortly.

> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index f804b76cde44..9c768b954264 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -144,14 +144,14 @@ LSM_HOOK(int, 0, inode_setattr, struct mnt_idmap *idmap, struct dentry *dentry,
>  LSM_HOOK(void, LSM_RET_VOID, inode_post_setattr, struct mnt_idmap *idmap,
>          struct dentry *dentry, int ia_valid)
>  LSM_HOOK(int, 0, inode_getattr, const struct path *path)
> -LSM_HOOK(int, 0, inode_setxattr, struct mnt_idmap *idmap,
> +LSM_HOOK(int, 1, inode_setxattr, struct mnt_idmap *idmap,
>          struct dentry *dentry, const char *name, const void *value,
>          size_t size, int flags)
>  LSM_HOOK(void, LSM_RET_VOID, inode_post_setxattr, struct dentry *dentry,
>          const char *name, const void *value, size_t size, int flags)
>  LSM_HOOK(int, 0, inode_getxattr, struct dentry *dentry, const char *name)
>  LSM_HOOK(int, 0, inode_listxattr, struct dentry *dentry)
> -LSM_HOOK(int, 0, inode_removexattr, struct mnt_idmap *idmap,
> +LSM_HOOK(int, 1, inode_removexattr, struct mnt_idmap *idmap,
>          struct dentry *dentry, const char *name)
>  LSM_HOOK(void, LSM_RET_VOID, inode_post_removexattr, struct dentry *dentry,
>          const char *name)
> --
> 2.34.1

-- 
paul-moore.com