From 20d4e80d255dd7cfecb53743bc550ebcad04549d Mon Sep 17 00:00:00 2001 From: John Johansen Date: Wed, 18 Dec 2019 11:04:07 -0800 Subject: [PATCH] apparmor: only get a label reference if the fast path check fails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The common fast path check can be done under rcu_read_lock() and doesn't need a reference count on the label. Only take a reference count if entering the slow path. Fixes reported hackbench regression - sha1 79e178a57dae ("Merge tag 'apparmor-pr-2019-12-03' of git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor") hackbench -l (256000/#grp) -g #grp 128 groups 19.679 ±0.90% - previous sha1 01d1dff64662 ("Merge tag 's390-5.5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux") hackbench -l (256000/#grp) -g #grp 128 groups 3.1689 ±3.04% Reported-by: Vincent Guittot Tested-by: Vincent Guittot Tested-by: Sebastian Andrzej Siewior Fixes: bce4e7e9c45e ("apparmor: reduce rcu_read_lock scope for aa_file_perm mediation") Signed-off-by: John Johansen --- security/apparmor/file.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/security/apparmor/file.c b/security/apparmor/file.c index fe2ebe5e865e..f1caf3674e1c 100644 --- a/security/apparmor/file.c +++ b/security/apparmor/file.c @@ -618,8 +618,7 @@ int aa_file_perm(const char *op, struct aa_label *label, struct file *file, fctx = file_ctx(file); rcu_read_lock(); - flabel = aa_get_newest_label(rcu_dereference(fctx->label)); - rcu_read_unlock(); + flabel = rcu_dereference(fctx->label); AA_BUG(!flabel); /* revalidate access, if task is unconfined, or the cached cred @@ -631,9 +630,13 @@ int aa_file_perm(const char *op, struct aa_label *label, struct file *file, */ denied = request & ~fctx->allow; if (unconfined(label) || unconfined(flabel) || - (!denied && aa_label_is_subset(flabel, label))) + (!denied && aa_label_is_subset(flabel, label))) { + rcu_read_unlock(); goto done; + } + flabel = aa_get_newest_label(flabel); + rcu_read_unlock(); /* TODO: label cross check */ if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry)) @@ -643,8 +646,9 @@ int aa_file_perm(const char *op, struct aa_label *label, struct file *file, else if (S_ISSOCK(file_inode(file)->i_mode)) error = __file_sock_perm(op, label, flabel, file, request, denied); -done: aa_put_label(flabel); + +done: return error; }