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| author | John Johansen <john.johansen@canonical.com> | 2019-12-18 11:04:07 -0800 |
|---|---|---|
| committer | John Johansen <john.johansen@canonical.com> | 2020-01-02 05:31:40 -0800 |
| commit | 20d4e80d255dd7cfecb53743bc550ebcad04549d (patch) | |
| tree | c740dec5f800df330c303db8018620b8bb0371f1 | |
| parent | 9c95a278ba7ca3ccc111c165cc74cb23c744fc85 (diff) | |
| download | lwn-20d4e80d255dd7cfecb53743bc550ebcad04549d.tar.gz lwn-20d4e80d255dd7cfecb53743bc550ebcad04549d.zip | |
apparmor: only get a label reference if the fast path check fails
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 <vincent.guittot@linaro.org>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Fixes: bce4e7e9c45e ("apparmor: reduce rcu_read_lock scope for aa_file_perm mediation")
Signed-off-by: John Johansen <john.johansen@canonical.com>
| -rw-r--r-- | security/apparmor/file.c | 12 |
1 files 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; } |