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Date:   Mon, 27 Jul 2020 14:41:27 +0200
From:   Jan Kara <jack@suse.cz>
To:     Christoph Hellwig <hch@lst.de>
Cc:     x86@kernel.org, Jan Kara <jack@suse.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-api@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH 4/4] quota: simplify the quotactl compat handling
Message-ID: <20200727124127.GO23179@quack2.suse.cz>
References: <20200726160401.311569-1-hch@lst.de>
 <20200726160401.311569-5-hch@lst.de>
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On Sun 26-07-20 18:04:01, Christoph Hellwig wrote:
> Fold the misaligned u64 workarounds into the main quotactl flow instead
> of implementing a separate compat syscall handler.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

The patch looks good to me and it saves a lot of boiler-plate code so feel
free to add:

Acked-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  arch/x86/entry/syscalls/syscall_32.tbl |   2 +-
>  fs/quota/Kconfig                       |   5 --
>  fs/quota/Makefile                      |   1 -
>  fs/quota/compat.c                      | 120 -------------------------
>  fs/quota/compat.h                      |  34 +++++++
>  fs/quota/quota.c                       |  73 ++++++++++++---
>  include/linux/quotaops.h               |   3 -
>  kernel/sys_ni.c                        |   1 -
>  8 files changed, 94 insertions(+), 145 deletions(-)
>  delete mode 100644 fs/quota/compat.c
>  create mode 100644 fs/quota/compat.h
> 
> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
> index d8f8a1a69ed11f..41d442d7c2db67 100644
> --- a/arch/x86/entry/syscalls/syscall_32.tbl
> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> @@ -142,7 +142,7 @@
>  128	i386	init_module		sys_init_module
>  129	i386	delete_module		sys_delete_module
>  130	i386	get_kernel_syms
> -131	i386	quotactl		sys_quotactl			compat_sys_quotactl32
> +131	i386	quotactl		sys_quotactl
>  132	i386	getpgid			sys_getpgid
>  133	i386	fchdir			sys_fchdir
>  134	i386	bdflush			sys_bdflush
> diff --git a/fs/quota/Kconfig b/fs/quota/Kconfig
> index 7218314ca13f00..4f5bb85099a904 100644
> --- a/fs/quota/Kconfig
> +++ b/fs/quota/Kconfig
> @@ -70,8 +70,3 @@ config QFMT_V2
>  config QUOTACTL
>  	bool
>  	default n
> -
> -config QUOTACTL_COMPAT
> -	bool
> -	depends on QUOTACTL && COMPAT_FOR_U64_ALIGNMENT
> -	default y
> diff --git a/fs/quota/Makefile b/fs/quota/Makefile
> index f2b49d0f0287c9..9160639daffa75 100644
> --- a/fs/quota/Makefile
> +++ b/fs/quota/Makefile
> @@ -4,5 +4,4 @@ obj-$(CONFIG_QFMT_V1)		+= quota_v1.o
>  obj-$(CONFIG_QFMT_V2)		+= quota_v2.o
>  obj-$(CONFIG_QUOTA_TREE)	+= quota_tree.o
>  obj-$(CONFIG_QUOTACTL)		+= quota.o kqid.o
> -obj-$(CONFIG_QUOTACTL_COMPAT)	+= compat.o
>  obj-$(CONFIG_QUOTA_NETLINK_INTERFACE)	+= netlink.o
> diff --git a/fs/quota/compat.c b/fs/quota/compat.c
> deleted file mode 100644
> index c305728576193d..00000000000000
> --- a/fs/quota/compat.c
> +++ /dev/null
> @@ -1,120 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -
> -#include <linux/syscalls.h>
> -#include <linux/compat.h>
> -#include <linux/quotaops.h>
> -
> -/*
> - * This code works only for 32 bit quota tools over 64 bit OS (x86_64, ia64)
> - * and is necessary due to alignment problems.
> - */
> -struct compat_if_dqblk {
> -	compat_u64 dqb_bhardlimit;
> -	compat_u64 dqb_bsoftlimit;
> -	compat_u64 dqb_curspace;
> -	compat_u64 dqb_ihardlimit;
> -	compat_u64 dqb_isoftlimit;
> -	compat_u64 dqb_curinodes;
> -	compat_u64 dqb_btime;
> -	compat_u64 dqb_itime;
> -	compat_uint_t dqb_valid;
> -};
> -
> -/* XFS structures */
> -struct compat_fs_qfilestat {
> -	compat_u64 dqb_bhardlimit;
> -	compat_u64 qfs_nblks;
> -	compat_uint_t qfs_nextents;
> -};
> -
> -struct compat_fs_quota_stat {
> -	__s8		qs_version;
> -	__u16		qs_flags;
> -	__s8		qs_pad;
> -	struct compat_fs_qfilestat	qs_uquota;
> -	struct compat_fs_qfilestat	qs_gquota;
> -	compat_uint_t	qs_incoredqs;
> -	compat_int_t	qs_btimelimit;
> -	compat_int_t	qs_itimelimit;
> -	compat_int_t	qs_rtbtimelimit;
> -	__u16		qs_bwarnlimit;
> -	__u16		qs_iwarnlimit;
> -};
> -
> -COMPAT_SYSCALL_DEFINE4(quotactl32, unsigned int, cmd,
> -		       const char __user *, special, qid_t, id,
> -		       void __user *, addr)
> -{
> -	unsigned int cmds;
> -	struct if_dqblk __user *dqblk;
> -	struct compat_if_dqblk __user *compat_dqblk;
> -	struct fs_quota_stat __user *fsqstat;
> -	struct compat_fs_quota_stat __user *compat_fsqstat;
> -	compat_uint_t data;
> -	u16 xdata;
> -	long ret;
> -
> -	cmds = cmd >> SUBCMDSHIFT;
> -
> -	switch (cmds) {
> -	case Q_GETQUOTA:
> -		dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
> -		compat_dqblk = addr;
> -		ret = kernel_quotactl(cmd, special, id, dqblk);
> -		if (ret)
> -			break;
> -		if (copy_in_user(compat_dqblk, dqblk, sizeof(*compat_dqblk)) ||
> -			get_user(data, &dqblk->dqb_valid) ||
> -			put_user(data, &compat_dqblk->dqb_valid))
> -			ret = -EFAULT;
> -		break;
> -	case Q_SETQUOTA:
> -		dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
> -		compat_dqblk = addr;
> -		ret = -EFAULT;
> -		if (copy_in_user(dqblk, compat_dqblk, sizeof(*compat_dqblk)) ||
> -			get_user(data, &compat_dqblk->dqb_valid) ||
> -			put_user(data, &dqblk->dqb_valid))
> -			break;
> -		ret = kernel_quotactl(cmd, special, id, dqblk);
> -		break;
> -	case Q_XGETQSTAT:
> -		fsqstat = compat_alloc_user_space(sizeof(struct fs_quota_stat));
> -		compat_fsqstat = addr;
> -		ret = kernel_quotactl(cmd, special, id, fsqstat);
> -		if (ret)
> -			break;
> -		ret = -EFAULT;
> -		/* Copying qs_version, qs_flags, qs_pad */
> -		if (copy_in_user(compat_fsqstat, fsqstat,
> -			offsetof(struct compat_fs_quota_stat, qs_uquota)))
> -			break;
> -		/* Copying qs_uquota */
> -		if (copy_in_user(&compat_fsqstat->qs_uquota,
> -			&fsqstat->qs_uquota,
> -			sizeof(compat_fsqstat->qs_uquota)) ||
> -			get_user(data, &fsqstat->qs_uquota.qfs_nextents) ||
> -			put_user(data, &compat_fsqstat->qs_uquota.qfs_nextents))
> -			break;
> -		/* Copying qs_gquota */
> -		if (copy_in_user(&compat_fsqstat->qs_gquota,
> -			&fsqstat->qs_gquota,
> -			sizeof(compat_fsqstat->qs_gquota)) ||
> -			get_user(data, &fsqstat->qs_gquota.qfs_nextents) ||
> -			put_user(data, &compat_fsqstat->qs_gquota.qfs_nextents))
> -			break;
> -		/* Copying the rest */
> -		if (copy_in_user(&compat_fsqstat->qs_incoredqs,
> -			&fsqstat->qs_incoredqs,
> -			sizeof(struct compat_fs_quota_stat) -
> -			offsetof(struct compat_fs_quota_stat, qs_incoredqs)) ||
> -			get_user(xdata, &fsqstat->qs_iwarnlimit) ||
> -			put_user(xdata, &compat_fsqstat->qs_iwarnlimit))
> -			break;
> -		ret = 0;
> -		break;
> -	default:
> -		ret = kernel_quotactl(cmd, special, id, addr);
> -	}
> -	return ret;
> -}
> diff --git a/fs/quota/compat.h b/fs/quota/compat.h
> new file mode 100644
> index 00000000000000..ef7d1e12d650b3
> --- /dev/null
> +++ b/fs/quota/compat.h
> @@ -0,0 +1,34 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/compat.h>
> +
> +struct compat_if_dqblk {
> +	compat_u64			dqb_bhardlimit;
> +	compat_u64			dqb_bsoftlimit;
> +	compat_u64			dqb_curspace;
> +	compat_u64			dqb_ihardlimit;
> +	compat_u64			dqb_isoftlimit;
> +	compat_u64			dqb_curinodes;
> +	compat_u64			dqb_btime;
> +	compat_u64			dqb_itime;
> +	compat_uint_t			dqb_valid;
> +};
> +
> +struct compat_fs_qfilestat {
> +	compat_u64			dqb_bhardlimit;
> +	compat_u64			qfs_nblks;
> +	compat_uint_t			qfs_nextents;
> +};
> +
> +struct compat_fs_quota_stat {
> +	__s8				qs_version;
> +	__u16				qs_flags;
> +	__s8				qs_pad;
> +	struct compat_fs_qfilestat	qs_uquota;
> +	struct compat_fs_qfilestat	qs_gquota;
> +	compat_uint_t			qs_incoredqs;
> +	compat_int_t			qs_btimelimit;
> +	compat_int_t			qs_itimelimit;
> +	compat_int_t			qs_rtbtimelimit;
> +	__u16				qs_bwarnlimit;
> +	__u16				qs_iwarnlimit;
> +};
> diff --git a/fs/quota/quota.c b/fs/quota/quota.c
> index 5444d3c4d93f37..e1e9d05a14c3e4 100644
> --- a/fs/quota/quota.c
> +++ b/fs/quota/quota.c
> @@ -19,6 +19,7 @@
>  #include <linux/types.h>
>  #include <linux/writeback.h>
>  #include <linux/nospec.h>
> +#include "compat.h"
>  
>  static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
>  				     qid_t id)
> @@ -211,8 +212,18 @@ static int quota_getquota(struct super_block *sb, int type, qid_t id,
>  	if (ret)
>  		return ret;
>  	copy_to_if_dqblk(&idq, &fdq);
> -	if (copy_to_user(addr, &idq, sizeof(idq)))
> -		return -EFAULT;
> +
> +	if (compat_need_64bit_alignment_fixup()) {
> +		struct compat_if_dqblk __user *compat_dqblk = addr;
> +
> +		if (copy_to_user(compat_dqblk, &idq, sizeof(*compat_dqblk)))
> +			return -EFAULT;
> +		if (put_user(idq.dqb_valid, &compat_dqblk->dqb_valid))
> +			return -EFAULT;
> +	} else {
> +		if (copy_to_user(addr, &idq, sizeof(idq)))
> +			return -EFAULT;
> +	}
>  	return 0;
>  }
>  
> @@ -277,8 +288,16 @@ static int quota_setquota(struct super_block *sb, int type, qid_t id,
>  	struct if_dqblk idq;
>  	struct kqid qid;
>  
> -	if (copy_from_user(&idq, addr, sizeof(idq)))
> -		return -EFAULT;
> +	if (compat_need_64bit_alignment_fixup()) {
> +		struct compat_if_dqblk __user *compat_dqblk = addr;
> +
> +		if (copy_from_user(&idq, compat_dqblk, sizeof(*compat_dqblk)) ||
> +		    get_user(idq.dqb_valid, &compat_dqblk->dqb_valid))
> +			return -EFAULT;
> +	} else {
> +		if (copy_from_user(&idq, addr, sizeof(idq)))
> +			return -EFAULT;
> +	}
>  	if (!sb->s_qcop->set_dqblk)
>  		return -ENOSYS;
>  	qid = make_kqid(current_user_ns(), type, id);
> @@ -382,6 +401,33 @@ static int quota_getstate(struct super_block *sb, int type,
>  	return 0;
>  }
>  
> +static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to,
> +		struct fs_qfilestat *from)
> +{
> +	if (copy_to_user(to, from, sizeof(*to)) ||
> +	    put_user(from->qfs_nextents, &to->qfs_nextents))
> +		return -EFAULT;
> +	return 0;
> +}
> +
> +static int compat_copy_fs_quota_stat(struct compat_fs_quota_stat __user *to,
> +		struct fs_quota_stat *from)
> +{
> +	if (put_user(from->qs_version, &to->qs_version) ||
> +	    put_user(from->qs_flags, &to->qs_flags) ||
> +	    put_user(from->qs_pad, &to->qs_pad) ||
> +	    compat_copy_fs_qfilestat(&to->qs_uquota, &from->qs_uquota) ||
> +	    compat_copy_fs_qfilestat(&to->qs_gquota, &from->qs_gquota) ||
> +	    put_user(from->qs_incoredqs, &to->qs_incoredqs) ||
> +	    put_user(from->qs_btimelimit, &to->qs_btimelimit) ||
> +	    put_user(from->qs_itimelimit, &to->qs_itimelimit) ||
> +	    put_user(from->qs_rtbtimelimit, &to->qs_rtbtimelimit) ||
> +	    put_user(from->qs_bwarnlimit, &to->qs_bwarnlimit) ||
> +	    put_user(from->qs_iwarnlimit, &to->qs_iwarnlimit))
> +		return -EFAULT;
> +	return 0;
> +}
> +
>  static int quota_getxstate(struct super_block *sb, int type, void __user *addr)
>  {
>  	struct fs_quota_stat fqs;
> @@ -390,9 +436,14 @@ static int quota_getxstate(struct super_block *sb, int type, void __user *addr)
>  	if (!sb->s_qcop->get_state)
>  		return -ENOSYS;
>  	ret = quota_getstate(sb, type, &fqs);
> -	if (!ret && copy_to_user(addr, &fqs, sizeof(fqs)))
> +	if (ret)
> +		return ret;
> +
> +	if (compat_need_64bit_alignment_fixup())
> +		return compat_copy_fs_quota_stat(addr, &fqs);
> +	if (copy_to_user(addr, &fqs, sizeof(fqs)))
>  		return -EFAULT;
> -	return ret;
> +	return 0;
>  }
>  
>  static int quota_getstatev(struct super_block *sb, int type,
> @@ -816,8 +867,8 @@ static struct super_block *quotactl_block(const char __user *special, int cmd)
>   * calls. Maybe we need to add the process quotas etc. in the future,
>   * but we probably should use rlimits for that.
>   */
> -int kernel_quotactl(unsigned int cmd, const char __user *special,
> -		    qid_t id, void __user *addr)
> +SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
> +		qid_t, id, void __user *, addr)
>  {
>  	uint cmds, type;
>  	struct super_block *sb = NULL;
> @@ -871,9 +922,3 @@ int kernel_quotactl(unsigned int cmd, const char __user *special,
>  		path_put(pathp);
>  	return ret;
>  }
> -
> -SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
> -		qid_t, id, void __user *, addr)
> -{
> -	return kernel_quotactl(cmd, special, id, addr);
> -}
> diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
> index 9cf0cd3dc88c68..a0f6668924d3ef 100644
> --- a/include/linux/quotaops.h
> +++ b/include/linux/quotaops.h
> @@ -27,9 +27,6 @@ static inline bool is_quota_modification(struct inode *inode, struct iattr *ia)
>  		(ia->ia_valid & ATTR_GID && !gid_eq(ia->ia_gid, inode->i_gid));
>  }
>  
> -int kernel_quotactl(unsigned int cmd, const char __user *special,
> -		    qid_t id, void __user *addr);
> -
>  #if defined(CONFIG_QUOTA)
>  
>  #define quota_error(sb, fmt, args...) \
> diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
> index 3b69a560a7ac56..f01b91cc57fa00 100644
> --- a/kernel/sys_ni.c
> +++ b/kernel/sys_ni.c
> @@ -370,7 +370,6 @@ COND_SYSCALL_COMPAT(fanotify_mark);
>  /* x86 */
>  COND_SYSCALL(vm86old);
>  COND_SYSCALL(modify_ldt);
> -COND_SYSCALL_COMPAT(quotactl32);
>  COND_SYSCALL(vm86);
>  COND_SYSCALL(kexec_file_load);
>  
> -- 
> 2.27.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR