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Date: Wed, 4 Feb 2015 09:01:57 +0100
From: Michael Kerrisk <mtk.manpages@...il.com>
To: Alexander Holler <holler@...oftware.de>
Cc: Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
Linux Kernel <linux-kernel@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH 1/5] WIP: Add syscall unlinkat_s (currently x86* only)
[CC += linux-api@]
On Mon, Feb 2, 2015 at 6:05 PM, Alexander Holler <holler@...oftware.de> wrote:
> Signed-off-by: Alexander Holler <holler@...oftware.de>
> ---
> arch/x86/syscalls/syscall_32.tbl | 1 +
> arch/x86/syscalls/syscall_64.tbl | 1 +
> fs/namei.c | 38 ++++++++++++++++++++++++++++++-----
> include/asm-generic/audit_dir_write.h | 1 +
> include/linux/fs.h | 1 +
> include/linux/syscalls.h | 1 +
> include/uapi/asm-generic/unistd.h | 4 +++-
> tools/perf/builtin-trace.c | 2 ++
> 8 files changed, 43 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
> index 9fe1b5d..7a3d530 100644
> --- a/arch/x86/syscalls/syscall_32.tbl
> +++ b/arch/x86/syscalls/syscall_32.tbl
> @@ -364,3 +364,4 @@
> 355 i386 getrandom sys_getrandom
> 356 i386 memfd_create sys_memfd_create
> 357 i386 bpf sys_bpf
> +359 i386 unlinkat_s sys_unlinkat_s
> diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
> index 281150b..97eaf01 100644
> --- a/arch/x86/syscalls/syscall_64.tbl
> +++ b/arch/x86/syscalls/syscall_64.tbl
> @@ -328,6 +328,7 @@
> 319 common memfd_create sys_memfd_create
> 320 common kexec_file_load sys_kexec_file_load
> 321 common bpf sys_bpf
> +322 common unlinkat_s sys_unlinkat_s
>
> #
> # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/fs/namei.c b/fs/namei.c
> index db5fe86..1ad3724 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3717,7 +3717,7 @@ EXPORT_SYMBOL(vfs_unlink);
> * writeout happening, and we don't want to prevent access to the directory
> * while waiting on the I/O.
> */
> -static long do_unlinkat(int dfd, const char __user *pathname)
> +static long do_unlinkat(int dfd, const char __user *pathname, bool secure)
> {
> int error;
> struct filename *name;
> @@ -3759,8 +3759,25 @@ exit2:
> dput(dentry);
> }
> mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
> - if (inode)
> - iput(inode); /* truncate the inode here */
> + if (inode) {
> + // TODO:
> + // if (inode is file and 's' flag is set)
> + // secure = true;
> + if (!secure)
> + iput(inode); /* truncate the inode here */
> + else {
> + struct super_block *sb = inode->i_sb;
> + if (sb->s_op->set_secure_delete)
> + sb->s_op->set_secure_delete(sb, true);
> + // TODO: We should fail if secure isn't supported,
> + // look up how that's possible here.
> + iput(inode); /* truncate the inode here */
> + // TODO: check if sb is still valid after the inode is gone
> + sync_filesystem(sb);
> + if (sb->s_op->set_secure_delete)
> + sb->s_op->set_secure_delete(sb, false);
> + }
> + }
> inode = NULL;
> if (delegated_inode) {
> error = break_deleg_wait(&delegated_inode);
> @@ -3796,12 +3813,23 @@ SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
> if (flag & AT_REMOVEDIR)
> return do_rmdir(dfd, pathname);
>
> - return do_unlinkat(dfd, pathname);
> + return do_unlinkat(dfd, pathname, false);
> }
>
> SYSCALL_DEFINE1(unlink, const char __user *, pathname)
> {
> - return do_unlinkat(AT_FDCWD, pathname);
> + return do_unlinkat(AT_FDCWD, pathname, false);
> +}
> +
> +SYSCALL_DEFINE3(unlinkat_s, int, dfd, const char __user *, pathname, int, flag)
> +{
> + if ((flag & ~AT_REMOVEDIR) != 0)
> + return -EINVAL;
> +
> + if (flag & AT_REMOVEDIR)
> + return do_rmdir(dfd, pathname);
> +
> + return do_unlinkat(dfd, pathname, true);
> }
>
> int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
> diff --git a/include/asm-generic/audit_dir_write.h b/include/asm-generic/audit_dir_write.h
> index 7b61db4..5282aba 100644
> --- a/include/asm-generic/audit_dir_write.h
> +++ b/include/asm-generic/audit_dir_write.h
> @@ -29,4 +29,5 @@ __NR_unlinkat,
> __NR_renameat,
> __NR_linkat,
> __NR_symlinkat,
> +__NR_unlinkat_s,
> #endif
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9ab779e..039e969 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1594,6 +1594,7 @@ struct super_operations {
> int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
> long (*nr_cached_objects)(struct super_block *, int);
> long (*free_cached_objects)(struct super_block *, long, int);
> + void (*set_secure_delete) (struct super_block *, bool);
> };
>
> /*
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index bda9b81..b88019b 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -877,4 +877,5 @@ asmlinkage long sys_seccomp(unsigned int op, unsigned int flags,
> asmlinkage long sys_getrandom(char __user *buf, size_t count,
> unsigned int flags);
> asmlinkage long sys_bpf(int cmd, union bpf_attr *attr, unsigned int size);
> +asmlinkage long sys_unlinkat_s(int dfd, const char __user * pathname, int flag);
> #endif
> diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
> index 22749c1..2ba072e 100644
> --- a/include/uapi/asm-generic/unistd.h
> +++ b/include/uapi/asm-generic/unistd.h
> @@ -707,9 +707,11 @@ __SYSCALL(__NR_getrandom, sys_getrandom)
> __SYSCALL(__NR_memfd_create, sys_memfd_create)
> #define __NR_bpf 280
> __SYSCALL(__NR_bpf, sys_bpf)
> +#define __NR_unlinkat_s 281
> +__SYSCALL(__NR_unlinkat_s, sys_unlinkat_s)
>
> #undef __NR_syscalls
> -#define __NR_syscalls 281
> +#define __NR_syscalls 282
>
> /*
> * All syscalls below here should go away really,
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index fb12645..1507335 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -1110,6 +1110,8 @@ static struct syscall_fmt {
> { .name = "uname", .errmsg = true, .alias = "newuname", },
> { .name = "unlinkat", .errmsg = true,
> .arg_scnprintf = { [0] = SCA_FDAT, /* dfd */ }, },
> + { .name = "unlinkat_s", .errmsg = true,
> + .arg_scnprintf = { [0] = SCA_FDAT, /* dfd */ }, },
> { .name = "utimensat", .errmsg = true,
> .arg_scnprintf = { [0] = SCA_FDAT, /* dirfd */ }, },
> { .name = "write", .errmsg = true,
> --
> 2.1.0
>
> --
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--
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/
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