2.4: Restore current->files in flush_old_exec
diff mbox series

Message ID 20030809011116.GB10487@gondor.apana.org.au
State New, archived
Headers show
Series
  • 2.4: Restore current->files in flush_old_exec
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Commit Message

Herbert Xu Aug. 9, 2003, 1:11 a.m. UTC
Hi:

The unshare_files patch to flush_old_exec() did not restore the original
state when exec_mmap fails.  This patch fixes that.

At this point, I believe the unshare_files stuff should be fine from
a correctness point of view.  However, there is still a performance
problem as every ELF exec call ends up dupliating the files structure
as well as walking through all file locks.

Cheers,

Comments

Andreas Gruenbacher Aug. 9, 2003, 1:48 a.m. UTC | #1
On Sat, 9 Aug 2003, Herbert Xu wrote:

> Hi:
>
> The unshare_files patch to flush_old_exec() did not restore the original
> state when exec_mmap fails.  This patch fixes that.

Indeed. This is still needed.

> At this point, I believe the unshare_files stuff should be fine from
> a correctness point of view.  However, there is still a performance
> problem as every ELF exec call ends up dupliating the files structure
> as well as walking through all file locks.

Cheers,
Andreas.
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Herbert Xu Aug. 9, 2003, 1:48 a.m. UTC | #2
On Sat, Aug 09, 2003 at 11:11:16AM +1000, herbert wrote:
> 
> At this point, I believe the unshare_files stuff should be fine from
> a correctness point of view.  However, there is still a performance
> problem as every ELF exec call ends up dupliating the files structure
> as well as walking through all file locks.

Here is the patch that ensures files is only duplicated when necessary.
Andreas Gruenbacher Aug. 9, 2003, 2:20 a.m. UTC | #3
On Sat, 9 Aug 2003, Herbert Xu wrote:

> On Sat, Aug 09, 2003 at 11:11:16AM +1000, herbert wrote:
> >
> > At this point, I believe the unshare_files stuff should be fine from
> > a correctness point of view.  However, there is still a performance
> > problem as every ELF exec call ends up dupliating the files structure
> > as well as walking through all file locks.
>
> Here is the patch that ensures files is only duplicated when necessary.

This patch is correct but unnecessary: steal_locks already tests for this
condition.


Cheers,
Andreas.
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Herbert Xu Aug. 9, 2003, 2:53 a.m. UTC | #4
On Sat, Aug 09, 2003 at 04:20:38AM +0200, Andreas Gruenbacher wrote:
> On Sat, 9 Aug 2003, Herbert Xu wrote:
> 
> > On Sat, Aug 09, 2003 at 11:11:16AM +1000, herbert wrote:
> > >
> > > At this point, I believe the unshare_files stuff should be fine from
> > > a correctness point of view.  However, there is still a performance
> > > problem as every ELF exec call ends up dupliating the files structure
> > > as well as walking through all file locks.
> >
> > Here is the patch that ensures files is only duplicated when necessary.
> 
> This patch is correct but unnecessary: steal_locks already tests for this
> condition.

Yes but when you call unshare_files twice one of them will have to
copy.
Andreas Gruenbacher Aug. 9, 2003, 3:01 a.m. UTC | #5
On Sat, 9 Aug 2003, Herbert Xu wrote:

> On Sat, Aug 09, 2003 at 04:20:38AM +0200, Andreas Gruenbacher wrote:
> > On Sat, 9 Aug 2003, Herbert Xu wrote:
> >
> > > On Sat, Aug 09, 2003 at 11:11:16AM +1000, herbert wrote:
> > > >
> > > > At this point, I believe the unshare_files stuff should be fine from
> > > > a correctness point of view.  However, there is still a performance
> > > > problem as every ELF exec call ends up dupliating the files structure
> > > > as well as walking through all file locks.
> > >
> > > Here is the patch that ensures files is only duplicated when necessary.
> >
> > This patch is correct but unnecessary: steal_locks already tests for this
> > condition.
>
> Yes but when you call unshare_files twice one of them will have to
> copy.

I see---that happens through flush_old_exec.
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Andreas Gruenbacher Aug. 9, 2003, 3:19 a.m. UTC | #6
Here is an update ...

> On Sat, 9 Aug 2003, Herbert Xu wrote:
> > Yes but when you call unshare_files twice one of them will have to
> > copy.
Index: linux-2.4.22-rc2.orig/fs/exec.c
===================================================================
--- linux-2.4.22-rc2.orig.orig/fs/exec.c	2003-08-09 04:44:07.000000000 +0200
+++ linux-2.4.22-rc2.orig/fs/exec.c	2003-08-09 05:04:35.000000000 +0200
@@ -582,8 +582,6 @@ int flush_old_exec(struct linux_binprm *
 	retval = unshare_files();
 	if(retval)
 		goto flush_failed;
-	steal_locks(files, current->files);
-	put_files_struct(files);
 	
 	/* 
 	 * Release all of the old mmap stuff
@@ -592,6 +590,8 @@ int flush_old_exec(struct linux_binprm *
 	if (retval) goto mmap_failed;
 
 	/* This is the point of no return */
+	steal_locks(files);
+	put_files_struct(files);
 	release_old_signals(oldsig);
 
 	current->sas_ss_sp = current->sas_ss_size = 0;
@@ -629,6 +629,8 @@ int flush_old_exec(struct linux_binprm *
 	return 0;
 
 mmap_failed:
+	put_files_struct(current->files);
+	current->files = files;
 flush_failed:
 	spin_lock_irq(&current->sigmask_lock);
 	if (current->sig != oldsig) {
Index: linux-2.4.22-rc2.orig/include/linux/fs.h
===================================================================
--- linux-2.4.22-rc2.orig.orig/include/linux/fs.h	2003-08-09 04:44:07.000000000 +0200
+++ linux-2.4.22-rc2.orig/include/linux/fs.h	2003-08-09 05:04:35.000000000 +0200
@@ -674,7 +674,7 @@ extern int __get_lease(struct inode *ino
 extern time_t lease_get_mtime(struct inode *);
 extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
 extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
-extern void steal_locks(fl_owner_t from, fl_owner_t to);
+extern void steal_locks(fl_owner_t from);
 
 struct fasync_struct {
 	int	magic;
Index: linux-2.4.22-rc2.orig/fs/binfmt_elf.c
===================================================================
--- linux-2.4.22-rc2.orig.orig/fs/binfmt_elf.c	2003-08-09 04:44:07.000000000 +0200
+++ linux-2.4.22-rc2.orig/fs/binfmt_elf.c	2003-08-09 05:06:05.000000000 +0200
@@ -444,7 +444,7 @@ static int load_elf_binary(struct linux_
 	struct elfhdr interp_elf_ex;
   	struct exec interp_ex;
 	char passed_fileno[6];
-	struct files_struct *files, *ftmp;
+	struct files_struct *files;
 	
 	/* Get the exec-header */
 	elf_ex = *((struct elfhdr *) bprm->buf);
@@ -480,7 +480,10 @@ static int load_elf_binary(struct linux_
 	files = current->files;		/* Refcounted so ok */
 	if(unshare_files() < 0)
 		goto out_free_ph;
-	steal_locks(files, current->files);
+	if (files == current->files) {
+		put_files_struct(files);
+		files = NULL;
+	}
 
 	/* exec will make our files private anyway, but for the a.out
 	   loader stuff we need to do it earlier */
@@ -603,7 +606,11 @@ static int load_elf_binary(struct linux_
 		goto out_free_dentry;
 
 	/* Discard our unneeded old files struct */
-	put_files_struct(files);
+	if (files) {
+		steal_locks(files);
+		put_files_struct(files);
+		files = NULL;
+	}
 
 	/* OK, This is the point of no return */
 	current->mm->start_data = 0;
@@ -714,18 +721,16 @@ static int load_elf_binary(struct linux_
 			elf_entry = load_elf_interp(&interp_elf_ex,
 						    interpreter,
 						    &interp_load_addr);
-
-		allow_write_access(interpreter);
-		fput(interpreter);
-		kfree(elf_interpreter);
-
 		if (BAD_ADDR(elf_entry)) {
 			printk(KERN_ERR "Unable to load interpreter\n");
-			kfree(elf_phdata);
 			send_sig(SIGSEGV, current, 0);
 			retval = -ENOEXEC; /* Nobody gets to see this, but.. */
-			goto out;
+			goto out_free_dentry;
 		}
+
+		allow_write_access(interpreter);
+		fput(interpreter);
+		kfree(elf_interpreter);
 	}
 
 	kfree(elf_phdata);
@@ -811,10 +816,10 @@ out_free_interp:
 out_free_file:
 	sys_close(elf_exec_fileno);
 out_free_fh:
-	ftmp = current->files;
-	current->files = files;
-	steal_locks(ftmp, current->files);
-	put_files_struct(ftmp);
+	if (files) {
+		put_files_struct(current->files);
+		current->files = files;
+	}
 out_free_ph:
 	kfree(elf_phdata);
 	goto out;
Index: linux-2.4.22-rc2.orig/fs/locks.c
===================================================================
--- linux-2.4.22-rc2.orig.orig/fs/locks.c	2003-08-09 04:44:07.000000000 +0200
+++ linux-2.4.22-rc2.orig/fs/locks.c	2003-08-09 05:04:35.000000000 +0200
@@ -1937,11 +1937,11 @@ done:
 	return length;
 }
 
-void steal_locks(fl_owner_t from, fl_owner_t to)
+void steal_locks(fl_owner_t from)
 {
 	struct list_head *tmp;
 
-	if (from == to)
+	if (from == current->files)
 		return;
 
 	lock_kernel();
@@ -1949,7 +1949,7 @@ void steal_locks(fl_owner_t from, fl_own
 		struct file_lock *fl = list_entry(tmp, struct file_lock,
 						  fl_link);
 		if (fl->fl_owner == from)
-			fl->fl_owner = to;
+			fl->fl_owner = current->files;
 	}
 	unlock_kernel();
 }
Andreas Gruenbacher Aug. 9, 2003, 10:41 a.m. UTC | #7
Hi,

On Sat, 2003-08-09 at 12:05, Herbert Xu wrote:
> On Sat, Aug 09, 2003 at 05:54:32AM +0200, Andreas Gruenbacher wrote:
> > On Sat, 9 Aug 2003, Andreas Gruenbacher wrote:
> > 
> > > Here is an update ...
> > Do you agree that this is correct?
> 
> It looks OK to me.  However, I still think the BAD_ADDR change is
> unnecessary.

Very good, thanks. The BAD_ADDR change is indeed not required. It saves
a funtion call so I think we should keep it, but I don't mind so much.


Cheers,

Patch
diff mbox series

Index: kernel-source-2.4/fs/exec.c
===================================================================
RCS file: /home/gondolin/herbert/src/CVS/debian/kernel-source-2.4/fs/exec.c,v
retrieving revision 1.5
diff -u -r1.5 exec.c
--- kernel-source-2.4/fs/exec.c	26 Jul 2003 02:54:45 -0000	1.5
+++ kernel-source-2.4/fs/exec.c	9 Aug 2003 01:00:28 -0000
@@ -557,7 +557,7 @@ 
 	char * name;
 	int i, ch, retval;
 	struct signal_struct * oldsig;
-	struct files_struct * files;
+	struct files_struct *files, *ftmp;
 
 	/*
 	 * Make sure we have a private signal table
@@ -576,8 +576,6 @@ 
 	retval = unshare_files();
 	if(retval)
 		goto flush_failed;
-	steal_locks(files, current->files);
-	put_files_struct(files);
 	
 	/* 
 	 * Release all of the old mmap stuff
@@ -586,6 +584,8 @@ 
 	if (retval) goto mmap_failed;
 
 	/* This is the point of no return */
+	steal_locks(files, current->files);
+	put_files_struct(files);
 	release_old_signals(oldsig);
 
 	current->sas_ss_sp = current->sas_ss_size = 0;
@@ -623,6 +623,9 @@ 
 	return 0;
 
 mmap_failed:
+	ftmp = current->files;
+	current->files = files;
+	put_files_struct(ftmp);
 flush_failed:
 	spin_lock_irq(&current->sigmask_lock);
 	if (current->sig != oldsig) {