From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: "David Hildenbrand" <david@redhat.com>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
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"Shakeel Butt" <shakeelb@google.com>,
"Marco Elver" <elver@google.com>,
"Daniel Jordan" <daniel.m.jordan@oracle.com>,
"Nicolas Viennot" <Nicolas.Viennot@twosigma.com>,
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"Michal Hocko" <mhocko@suse.com>,
"Miklos Szeredi" <miklos@szeredi.hu>,
"Chengguang Xu" <cgxu519@mykernel.net>,
"Christian König" <ckoenig.leichtzumerken@gmail.com>,
linux-unionfs@vger.kernel.org, linux-api@vger.kernel.org,
x86@kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org
Subject: [PATCH v1 2/7] kernel/fork: factor out atomcially replacing the current MM exe_file
Date: Thu, 12 Aug 2021 10:43:43 +0200 [thread overview]
Message-ID: <20210812084348.6521-3-david@redhat.com> (raw)
In-Reply-To: <20210812084348.6521-1-david@redhat.com>
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>
---
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 8:44 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 ` David Hildenbrand [this message]
2021-08-12 9:17 ` [PATCH v1 2/7] kernel/fork: factor out atomcially replacing the current MM exe_file Christian Brauner
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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