The patch titled
Subject: exec: binfmt_misc: don't nullify Node->dentry in kill_node()
has been added to the -mm tree. Its filename is
exec-binfmt_misc-dont-nullify-node-dentry-in-kill_node.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/exec-binfmt_misc-dont-nullify-node-dentry-in-kill_node.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/exec-binfmt_misc-dont-nullify-node-dentry-in-kill_node.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: exec: binfmt_misc: don't nullify Node->dentry in kill_node()
kill_node() nullifies/checks Node->dentry to avoid double free. This
complicates the next changes and this is very confusing:
- we do not need to check dentry != NULL under entries_lock, kill_node()
is always called under inode_lock(d_inode(root)) and we rely on this
inode_lock() anyway, without this lock the MISC_FMT_OPEN_FILE cleanup
could race with itself.
- if kill_inode() was already called and ->dentry == NULL we should not
even try to close e->interp_file.
We can change bm_entry_write() to simply check !list_empty(list) before
kill_node. Again, we rely on inode_lock(), in particular it saves us from
the race with bm_status_write(), another caller of kill_node().
Link: http://lkml.kernel.org/r/20170922143641.GA17210@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Ben Woodard <woodard@xxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Jim Foraker <foraker1@xxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: <tdhooge@xxxxxxxx>
Cc: Travis Gummels <tgummels@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_misc.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)
diff -puN fs/binfmt_misc.c~exec-binfmt_misc-dont-nullify-node-dentry-in-kill_node fs/binfmt_misc.c
--- a/fs/binfmt_misc.c~exec-binfmt_misc-dont-nullify-node-dentry-in-kill_node
+++ a/fs/binfmt_misc.c
@@ -603,11 +603,7 @@ static void kill_node(Node *e)
struct dentry *dentry;
write_lock(&entries_lock);
- dentry = e->dentry;
- if (dentry) {
- list_del_init(&e->list);
- e->dentry = NULL;
- }
+ list_del_init(&e->list);
write_unlock(&entries_lock);
if ((e->flags & MISC_FMT_OPEN_FILE) && e->interp_file) {
@@ -615,12 +611,11 @@ static void kill_node(Node *e)
e->interp_file = NULL;
}
- if (dentry) {
- drop_nlink(d_inode(dentry));
- d_drop(dentry);
- dput(dentry);
- simple_release_fs(&bm_mnt, &entry_count);
- }
+ dentry = e->dentry;
+ drop_nlink(d_inode(dentry));
+ d_drop(dentry);
+ dput(dentry);
+ simple_release_fs(&bm_mnt, &entry_count);
}
/* /<entry> */
@@ -665,7 +660,8 @@ static ssize_t bm_entry_write(struct fil
root = file_inode(file)->i_sb->s_root;
inode_lock(d_inode(root));
- kill_node(e);
+ if (!list_empty(&e->list))
+ kill_node(e);
inode_unlock(d_inode(root));
break;
@@ -794,7 +790,7 @@ static ssize_t bm_status_write(struct fi
inode_lock(d_inode(root));
while (!list_empty(&entries))
- kill_node(list_entry(entries.next, Node, list));
+ kill_node(list_first_entry(&entries, Node, list));
inode_unlock(d_inode(root));
break;
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
exec-load_script-kill-the-onstack-interp-array.patch
exec-binfmt_misc-dont-nullify-node-dentry-in-kill_node.patch
exec-binfmt_misc-shift-filp_closeinterp_file-from-kill_node-to-bm_evict_inode.patch
exec-binfmt_misc-remove-the-confusing-e-interp_file-=-null-checks.patch
exec-binfmt_misc-fix-race-between-load_misc_binary-and-kill_node.patch
exec-binfmt_misc-kill-the-onstack-iname-array.patch
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