From: Christian Brauner <christian.brauner@ubuntu.com>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
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"Michal Hocko" <mhocko@suse.com>,
"Miklos Szeredi" <miklos@szeredi.hu>,
"Chengguang Xu" <cgxu519@mykernel.net>,
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linux-unionfs@vger.kernel.org, linux-api@vger.kernel.org,
x86@kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v1 2/7] kernel/fork: factor out atomcially replacing the current MM exe_file
Date: Thu, 12 Aug 2021 11:17:42 +0200 [thread overview]
Message-ID: <20210812091742.nbnmsa37adaqkxwd@wittgenstein> (raw)
In-Reply-To: <20210812084348.6521-3-david@redhat.com>
On Thu, Aug 12, 2021 at 10:43:43AM +0200, David Hildenbrand wrote:
> Let's factor the main logic out into atomic_set_mm_exe_file(), such that
> all mm->exe_file logic is contained in kernel/fork.c.
>
> While at it, perform some simple cleanups that are possible now that
> we're simplifying the individual functions.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
Looks good.
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
> include/linux/mm.h | 2 ++
> kernel/fork.c | 35 +++++++++++++++++++++++++++++++++--
> kernel/sys.c | 33 +--------------------------------
> 3 files changed, 36 insertions(+), 34 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 7ca22e6e694a..197505324b74 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2581,6 +2581,8 @@ extern int mm_take_all_locks(struct mm_struct *mm);
> extern void mm_drop_all_locks(struct mm_struct *mm);
>
> extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
> +extern int atomic_set_mm_exe_file(struct mm_struct *mm,
> + struct file *new_exe_file);
> extern struct file *get_mm_exe_file(struct mm_struct *mm);
> extern struct file *get_task_exe_file(struct task_struct *task);
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index bc94b2cc5995..6bd2e52bcdfb 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1149,8 +1149,8 @@ void mmput_async(struct mm_struct *mm)
> * Main users are mmput() and sys_execve(). Callers prevent concurrent
> * invocations: in mmput() nobody alive left, in execve task is single
> * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
> - * mm->exe_file, but does so without using set_mm_exe_file() in order
> - * to avoid the need for any locks.
> + * mm->exe_file, but uses atomic_set_mm_exe_file(), avoiding the need
> + * for any locks.
> */
> void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
> {
> @@ -1170,6 +1170,37 @@ void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
> fput(old_exe_file);
> }
>
> +int atomic_set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
> +{
> + struct vm_area_struct *vma;
> + struct file *old_exe_file;
> + int ret = 0;
> +
> + /* Forbid mm->exe_file change if old file still mapped. */
> + old_exe_file = get_mm_exe_file(mm);
> + if (old_exe_file) {
> + mmap_read_lock(mm);
> + for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
> + if (!vma->vm_file)
> + continue;
> + if (path_equal(&vma->vm_file->f_path,
> + &old_exe_file->f_path))
> + ret = -EBUSY;
> + }
> + mmap_read_unlock(mm);
> + fput(old_exe_file);
> + if (ret)
> + return ret;
> + }
> +
> + /* set the new file, lockless */
> + get_file(new_exe_file);
> + old_exe_file = xchg(&mm->exe_file, new_exe_file);
> + if (old_exe_file)
> + fput(old_exe_file);
> + return 0;
> +}
> +
> /**
> * get_mm_exe_file - acquire a reference to the mm's executable file
> *
> diff --git a/kernel/sys.c b/kernel/sys.c
> index ef1a78f5d71c..40551b411fda 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1846,7 +1846,6 @@ SYSCALL_DEFINE1(umask, int, mask)
> static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
> {
> struct fd exe;
> - struct file *old_exe, *exe_file;
> struct inode *inode;
> int err;
>
> @@ -1869,40 +1868,10 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
> if (err)
> goto exit;
>
> - /*
> - * Forbid mm->exe_file change if old file still mapped.
> - */
> - exe_file = get_mm_exe_file(mm);
> - err = -EBUSY;
> - if (exe_file) {
> - struct vm_area_struct *vma;
> -
> - mmap_read_lock(mm);
> - for (vma = mm->mmap; vma; vma = vma->vm_next) {
> - if (!vma->vm_file)
> - continue;
> - if (path_equal(&vma->vm_file->f_path,
> - &exe_file->f_path))
> - goto exit_err;
> - }
> -
> - mmap_read_unlock(mm);
> - fput(exe_file);
> - }
> -
> - err = 0;
> - /* set the new file, lockless */
> - get_file(exe.file);
> - old_exe = xchg(&mm->exe_file, exe.file);
> - if (old_exe)
> - fput(old_exe);
> + err = atomic_set_mm_exe_file(mm, exe.file);
> exit:
> fdput(exe);
> return err;
> -exit_err:
> - mmap_read_unlock(mm);
> - fput(exe_file);
> - goto exit;
> }
>
> /*
> --
> 2.31.1
>
next prev parent reply other threads:[~2021-08-12 9:18 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-12 8:43 [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 1/7] binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib() David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 2/7] kernel/fork: factor out atomcially replacing the current MM exe_file David Hildenbrand
2021-08-12 9:17 ` Christian Brauner [this message]
2021-08-12 8:43 ` [PATCH v1 3/7] kernel/fork: always deny write access to " David Hildenbrand
2021-08-12 10:05 ` Christian Brauner
2021-08-12 10:13 ` David Hildenbrand
2021-08-12 12:32 ` Christian Brauner
2021-08-12 12:38 ` David Hildenbrand
2021-08-12 16:51 ` Linus Torvalds
2021-08-12 19:38 ` David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 4/7] binfmt: remove in-tree usage of MAP_DENYWRITE David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 5/7] mm: remove VM_DENYWRITE David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 6/7] mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff() David Hildenbrand
2021-08-12 8:43 ` [PATCH v1 7/7] fs: update documentation of get_write_access() and friends David Hildenbrand
2021-08-12 12:20 ` [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE Florian Weimer
2021-08-12 12:47 ` David Hildenbrand
2021-08-12 16:17 ` Eric W. Biederman
2021-08-12 17:32 ` Eric W. Biederman
2021-08-12 17:35 ` Andy Lutomirski
2021-08-12 17:48 ` Eric W. Biederman
2021-08-12 18:01 ` Andy Lutomirski
2021-08-12 18:10 ` Linus Torvalds
2021-08-12 18:47 ` Eric W. Biederman
2021-08-13 9:05 ` David Laight
[not found] ` <87h7ft2j68.fsf@disp2133>
2021-08-13 20:51 ` Florian Weimer
2021-08-14 0:31 ` Linus Torvalds
2021-08-14 0:49 ` Andy Lutomirski
2021-08-14 0:54 ` Linus Torvalds
2021-08-14 0:58 ` Linus Torvalds
2021-08-14 1:57 ` Al Viro
2021-08-14 2:02 ` Al Viro
2021-08-14 9:06 ` David Hildenbrand
2021-08-14 7:53 ` Christian Brauner
2021-08-14 19:52 ` David Laight
2021-08-26 17:48 ` Andy Lutomirski
2021-08-26 21:47 ` David Hildenbrand
2021-08-26 22:13 ` Eric W. Biederman
2021-08-27 8:22 ` David Laight
2021-08-27 15:58 ` Eric W. Biederman
2021-09-01 8:28 ` David Hildenbrand
2021-08-27 10:18 ` Christian Brauner
2021-08-14 3:04 ` Matthew Wilcox
2021-08-17 16:48 ` Removing Mandatory Locks Eric W. Biederman
2021-08-17 16:50 ` David Hildenbrand
2021-08-18 9:34 ` Rodrigo Campos
2021-08-19 19:18 ` Jeff Layton
2021-08-19 20:03 ` Willy Tarreau
2021-08-19 18:39 ` Jeff Layton
2021-08-19 19:15 ` Linus Torvalds
2021-08-19 19:55 ` Eric Biggers
2021-08-19 20:18 ` Jeff Layton
2021-08-19 20:31 ` Linus Torvalds
2021-08-19 21:43 ` Jeff Layton
2021-08-19 22:32 ` Linus Torvalds
2021-08-20 8:30 ` David Laight
2021-08-23 7:55 ` Geert Uytterhoeven
2021-08-23 8:14 ` David Laight
2021-08-20 13:43 ` Steven Rostedt
2021-08-20 16:06 ` Linus Torvalds
2021-08-20 2:10 ` Matthew Wilcox
2021-08-20 6:36 ` Amir Goldstein
2021-08-20 7:14 ` Amir Goldstein
2021-08-20 12:27 ` Jeff Layton
2021-08-20 12:38 ` Willy Tarreau
2021-08-20 13:03 ` Jeff Layton
2021-08-20 13:11 ` Willy Tarreau
2021-08-20 16:30 ` Kees Cook
2021-08-20 19:17 ` H. Peter Anvin
2021-08-20 21:29 ` Jeff Layton
2021-08-21 12:45 ` Jeff Layton
2021-08-23 22:15 ` J. Bruce Fields
2021-08-20 22:31 ` Matthew Wilcox
2021-08-18 7:51 ` [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE Christian Brauner
2021-08-18 15:42 ` J. Bruce Fields
2021-08-19 13:56 ` Eric W. Biederman
2021-08-19 14:33 ` J. Bruce Fields
2021-08-20 12:54 ` Jeff Layton
[not found] ` <162943109106.9892.7426782042253067338@noble.neil.brown.name>
2021-08-20 8:25 ` David Laight
2021-08-12 19:24 ` David Hildenbrand
2021-08-12 18:15 ` Florian Weimer
2021-08-12 18:21 ` Linus Torvalds
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