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apparmor: try to avoid refing the label in apparmor_file_open

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If the label is not stale (which is the common case), the fact that the
passed file object holds a reference can be leverged to avoid the
ref/unref cycle. Doing so reduces performance impact of apparmor on
parallel open() invocations.

When benchmarking on a 24-core vm using will-it-scale's open1_process
("Separate file open"), the results are (ops/s):
before: 6092196
after:  8309726 (+36%)

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
Mateusz Guzik 2024-06-20 19:15:27 +02:00 committed by John Johansen
parent 4b954a0255
commit f4fee216df
2 changed files with 23 additions and 2 deletions
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20
security/apparmor/include/cred.h
View file

@ -63,6 +63,26 @@ static inline struct aa_label *aa_get_newest_cred_label(const struct cred *cred)
return aa_get_newest_label(aa_cred_raw_label(cred));
}
static inline struct aa_label *aa_get_newest_cred_label_condref(const struct cred *cred,
bool *needput)
{
struct aa_label *l = aa_cred_raw_label(cred);
if (unlikely(label_is_stale(l))) {
*needput = true;
return aa_get_newest_label(l);
}
*needput = false;
return l;
}
static inline void aa_put_label_condref(struct aa_label *l, bool needput)
{
if (unlikely(needput))
aa_put_label(l);
}
/**
* aa_current_raw_label - find the current tasks confining label
*

5
security/apparmor/lsm.c
View file

@ -461,6 +461,7 @@ static int apparmor_file_open(struct file *file)
struct aa_file_ctx *fctx = file_ctx(file);
struct aa_label *label;
int error = 0;
bool needput;
if (!path_mediated_fs(file->f_path.dentry))
return 0;
@ -477,7 +478,7 @@ static int apparmor_file_open(struct file *file)
return 0;
}
label = aa_get_newest_cred_label(file->f_cred);
label = aa_get_newest_cred_label_condref(file->f_cred, &needput);
if (!unconfined(label)) {
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct inode *inode = file_inode(file);
@ -494,7 +495,7 @@ static int apparmor_file_open(struct file *file)
/* todo cache full allowed permissions set and state */
fctx->allow = aa_map_file_to_perms(file);
}
aa_put_label(label);
aa_put_label_condref(label, needput);
return error;
}