All of lore.kernel.org
 help / color / mirror / Atom feed
From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: David Hildenbrand <david@redhat.com>,
	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>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Kees Cook <keescook@chromium.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Greg Ungerer <gerg@linux-m68k.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Mike Rapoport <rppt@kernel.org>, Vlastimil Babka <vbabka@suse.cz>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Chinwen Chang <chinwen.chang@mediatek.com>,
	Michel Lespinasse <walken@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Huang Ying <ying.huang@intel.com>, Jann Horn <jannh@google.com>,
	Feng Tang <feng.tang@intel.com>,
	Kevin Brodsky <Kevin.Brodsky@arm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Shawn Anastasio <shawn@anastas.io>,
	Steven Price <steven.price@arm.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Jens Axboe <axboe@kernel.dk>,
	Gabriel Krisman Bertazi <krisman@collabora.com>,
	Peter Xu <peterx@redhat.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Shakeel Butt <shakeelb@google.com>,
	Marco Elver <elver@google.com>,
	Daniel Jordan <daniel.m.jordan@oracle.com>,
	Nicolas Viennot <Nicolas.Viennot@twosigma.com>,
	Thomas Cedeno <thomascedeno@google.com>,
	Collin Fijalkovich <cfijalkovich@google.com>,
	Michal Hocko <mhocko@suse.com>,
	linux-api@vger.kernel.org, x86@kernel.org,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH RFC 2/7] kernel/fork: factor out atomcially replacing the current MM exe_file
Date: Fri, 23 Apr 2021 15:16:35 +0200	[thread overview]
Message-ID: <20210423131640.20080-3-david@redhat.com> (raw)
In-Reply-To: <20210423131640.20080-1-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 8ba434287387..043702972e5f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2540,6 +2540,8 @@ 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 426cd0c51f9e..199463625adc 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1138,8 +1138,8 @@ 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 do 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)
 {
@@ -1159,6 +1159,37 @@ 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 2e2e3f378d97..7dcd9fb3153c 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1828,7 +1828,6 @@ 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;
 
@@ -1851,40 +1850,10 @@ 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;
 }
 
 /*
-- 
2.30.2


  parent reply	other threads:[~2021-04-23 13:17 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-23 13:16 [PATCH RFC 0/7] Remove in-tree usage of MAP_DENYWRITE David Hildenbrand
2021-04-23 13:16 ` [PATCH RFC 1/7] binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib() David Hildenbrand
2021-04-23 13:16 ` David Hildenbrand [this message]
2021-04-23 13:16 ` [PATCH RFC 3/7] kernel/fork: always deny write access to current MM exe_file David Hildenbrand
2021-04-23 13:16 ` [PATCH RFC 4/7] binfmt: remove in-tree usage of MAP_DENYWRITE David Hildenbrand
2021-04-23 13:16 ` [PATCH RFC 5/7] mm: remove VM_DENYWRITE David Hildenbrand
2021-04-23 13:16 ` [PATCH RFC 6/7] mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff() David Hildenbrand
2021-04-23 13:16 ` [PATCH RFC 7/7] fs: update documentation of get_write_access() and friends David Hildenbrand

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210423131640.20080-3-david@redhat.com \
    --to=david@redhat.com \
    --cc=Kevin.Brodsky@arm.com \
    --cc=Nicolas.Viennot@twosigma.com \
    --cc=acme@kernel.org \
    --cc=adobriyan@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=alexander.shishkin@linux.intel.com \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=axboe@kernel.dk \
    --cc=bp@alien8.de \
    --cc=catalin.marinas@arm.com \
    --cc=cfijalkovich@google.com \
    --cc=chinwen.chang@mediatek.com \
    --cc=christian.brauner@ubuntu.com \
    --cc=daniel.m.jordan@oracle.com \
    --cc=ebiederm@xmission.com \
    --cc=elver@google.com \
    --cc=feng.tang@intel.com \
    --cc=geert@linux-m68k.org \
    --cc=gerg@linux-m68k.org \
    --cc=hpa@zytor.com \
    --cc=jannh@google.com \
    --cc=jolsa@redhat.com \
    --cc=keescook@chromium.org \
    --cc=krisman@collabora.com \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux@rasmusvillemoes.dk \
    --cc=mark.rutland@arm.com \
    --cc=mhocko@suse.com \
    --cc=mingo@redhat.com \
    --cc=mpe@ellerman.id.au \
    --cc=namhyung@kernel.org \
    --cc=npiggin@gmail.com \
    --cc=peterx@redhat.com \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=rostedt@goodmis.org \
    --cc=rppt@kernel.org \
    --cc=sergey.senozhatsky@gmail.com \
    --cc=shakeelb@google.com \
    --cc=shawn@anastas.io \
    --cc=steven.price@arm.com \
    --cc=surenb@google.com \
    --cc=tglx@linutronix.de \
    --cc=thomascedeno@google.com \
    --cc=vbabka@suse.cz \
    --cc=vincenzo.frascino@arm.com \
    --cc=viro@zeniv.linux.org.uk \
    --cc=walken@google.com \
    --cc=willy@infradead.org \
    --cc=x86@kernel.org \
    --cc=ying.huang@intel.com \
    --subject='Re: [PATCH RFC 2/7] kernel/fork: factor out atomcially replacing the current MM exe_file' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.