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apparmor: Move path lookup to using preallocated buffers
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Dynamically allocating buffers is problematic and is an extra layer
that is a potntial point of failure and can slow down mediation.
Change path lookup to use the preallocated per cpu buffers.

Signed-off-by: John Johansen <[email protected]>
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John Johansen committed Jun 8, 2017
1 parent 72c8a76 commit 4227c33
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Showing 4 changed files with 53 additions and 86 deletions.
8 changes: 5 additions & 3 deletions security/apparmor/domain.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -357,15 +357,17 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
AA_BUG(!ctx);

profile = aa_get_newest_profile(ctx->profile);

/* buffer freed below, name is pointer into buffer */
get_buffers(buffer);
/*
* get the namespace from the replacement profile as replacement
* can change the namespace
*/
ns = profile->ns;
state = profile->file.start;

/* buffer freed below, name is pointer into buffer */
error = aa_path_name(&bprm->file->f_path, profile->path_flags, &buffer,
error = aa_path_name(&bprm->file->f_path, profile->path_flags, buffer,
&name, &info, profile->disconnected);
if (error) {
if (unconfined(profile) ||
Expand Down Expand Up @@ -515,7 +517,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
cleanup:
aa_put_profile(new_profile);
aa_put_profile(profile);
kfree(buffer);
put_buffers(buffer);

return error;
}
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13 changes: 7 additions & 6 deletions security/apparmor/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -285,7 +285,8 @@ int aa_path_perm(const char *op, struct aa_profile *profile,
int error;

flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
error = aa_path_name(path, flags, &buffer, &name, &info,
get_buffers(buffer);
error = aa_path_name(path, flags, buffer, &name, &info,
profile->disconnected);
if (error) {
if (error == -ENOENT && is_deleted(path->dentry)) {
Expand All @@ -304,7 +305,7 @@ int aa_path_perm(const char *op, struct aa_profile *profile,
}
error = aa_audit_file(profile, &perms, op, request, name, NULL,
cond->uid, info, error);
kfree(buffer);
put_buffers(buffer);

return error;
}
Expand Down Expand Up @@ -363,16 +364,17 @@ int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
unsigned int state;
int error;

get_buffers(buffer, buffer2);
lperms = nullperms;

/* buffer freed below, lname is pointer in buffer */
error = aa_path_name(&link, profile->path_flags, &buffer, &lname,
error = aa_path_name(&link, profile->path_flags, buffer, &lname,
&info, profile->disconnected);
if (error)
goto audit;

/* buffer2 freed below, tname is pointer in buffer2 */
error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
error = aa_path_name(&target, profile->path_flags, buffer2, &tname,
&info, profile->disconnected);
if (error)
goto audit;
Expand Down Expand Up @@ -432,8 +434,7 @@ int aa_path_link(struct aa_profile *profile, struct dentry *old_dentry,
audit:
error = aa_audit_file(profile, &lperms, OP_LINK, request,
lname, tname, cond.uid, info, error);
kfree(buffer);
kfree(buffer2);
put_buffers(buffer, buffer2);

return error;
}
Expand Down
4 changes: 2 additions & 2 deletions security/apparmor/include/path.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,10 +23,10 @@ enum path_flags {
PATH_CHROOT_NSCONNECT = 0x10, /* connect paths that are at ns root */

PATH_DELEGATE_DELETED = 0x08000, /* delegate deleted files */
PATH_MEDIATE_DELETED = 0x10000, /* mediate deleted paths */
PATH_MEDIATE_DELETED = 0x10000, /* mediate deleted paths */
};

int aa_path_name(const struct path *path, int flags, char **buffer,
int aa_path_name(const struct path *path, int flags, char *buffer,
const char **name, const char **info,
const char *disconnected);

Expand Down
114 changes: 39 additions & 75 deletions security/apparmor/path.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,6 @@ static int disconnect(const struct path *path, char *buf, char **name,
* d_namespace_path - lookup a name associated with a given path
* @path: path to lookup (NOT NULL)
* @buf: buffer to store path to (NOT NULL)
* @buflen: length of @buf
* @name: Returns - pointer for start of path name with in @buf (NOT NULL)
* @flags: flags controlling path lookup
* @disconnected: string to prefix to disconnected paths
Expand All @@ -90,12 +89,14 @@ static int disconnect(const struct path *path, char *buf, char **name,
* When no error the path name is returned in @name which points to
* to a position in @buf
*/
static int d_namespace_path(const struct path *path, char *buf, int buflen,
char **name, int flags, const char *disconnected)
static int d_namespace_path(const struct path *path, char *buf, char **name,
int flags, const char *disconnected)
{
char *res;
int error = 0;
int connected = 1;
int isdir = (flags & PATH_IS_DIR) ? 1 : 0;
int buflen = aa_g_path_max - isdir;

if (path->mnt->mnt_flags & MNT_INTERNAL) {
/* it's not mounted anywhere */
Expand All @@ -110,10 +111,12 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen,
/* TODO: convert over to using a per namespace
* control instead of hard coded /proc
*/
return prepend(name, *name - buf, "/proc", 5);
error = prepend(name, *name - buf, "/proc", 5);
goto out;
} else
return disconnect(path, buf, name, flags,
disconnected);
error = disconnect(path, buf, name, flags,
disconnected);
goto out;
}

/* resolve paths relative to chroot?*/
Expand All @@ -132,8 +135,11 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen,
* be returned.
*/
if (!res || IS_ERR(res)) {
if (PTR_ERR(res) == -ENAMETOOLONG)
return -ENAMETOOLONG;
if (PTR_ERR(res) == -ENAMETOOLONG) {
error = -ENAMETOOLONG;
*name = buf;
goto out;
}
connected = 0;
res = dentry_path_raw(path->dentry, buf, buflen);
if (IS_ERR(res)) {
Expand All @@ -146,69 +152,37 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen,

*name = res;

if (!connected)
error = disconnect(path, buf, name, flags, disconnected);

/* Handle two cases:
* 1. A deleted dentry && profile is not allowing mediation of deleted
* 2. On some filesystems, newly allocated dentries appear to the
* security_path hooks as a deleted dentry except without an inode
* allocated.
*/
if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
!(flags & PATH_MEDIATE_DELETED)) {
!(flags & (PATH_MEDIATE_DELETED | PATH_DELEGATE_DELETED))) {
error = -ENOENT;
goto out;
}

if (!connected)
error = disconnect(path, buf, name, flags, disconnected);

out:
return error;
}

/**
* get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
* @path: path to get name for (NOT NULL)
* @flags: flags controlling path lookup
* @buffer: buffer to put name in (NOT NULL)
* @size: size of buffer
* @name: Returns - contains position of path name in @buffer (NOT NULL)
*
* Returns: %0 else error on failure
*/
static int get_name_to_buffer(const struct path *path, int flags, char *buffer,
int size, char **name, const char **info,
const char *disconnected)
{
int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
int error = d_namespace_path(path, buffer, size - adjust, name, flags,
disconnected);

if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
/*
* Append "/" to the pathname. The root directory is a special
* case; it already ends in slash.
*/
strcpy(&buffer[size - 2], "/");

if (info && error) {
if (error == -ENOENT)
*info = "Failed name lookup - deleted entry";
else if (error == -EACCES)
*info = "Failed name lookup - disconnected path";
else if (error == -ENAMETOOLONG)
*info = "Failed name lookup - name too long";
else
*info = "Failed name lookup";
}
/*
* Append "/" to the pathname. The root directory is a special
* case; it already ends in slash.
*/
if (!error && isdir && ((*name)[1] != '\0' || (*name)[0] != '/'))
strcpy(&buf[aa_g_path_max - 2], "/");

return error;
}

/**
* aa_path_name - compute the pathname of a file
* aa_path_name - get the pathname to a buffer ensure dir / is appended
* @path: path the file (NOT NULL)
* @flags: flags controlling path name generation
* @buffer: buffer that aa_get_name() allocated (NOT NULL)
* @buffer: buffer to put name in (NOT NULL)
* @name: Returns - the generated path name if !error (NOT NULL)
* @info: Returns - information on why the path lookup failed (MAYBE NULL)
* @disconnected: string to prepend to disconnected paths
Expand All @@ -224,33 +198,23 @@ static int get_name_to_buffer(const struct path *path, int flags, char *buffer,
*
* Returns: %0 else error code if could retrieve name
*/
int aa_path_name(const struct path *path, int flags, char **buffer,
int aa_path_name(const struct path *path, int flags, char *buffer,
const char **name, const char **info, const char *disconnected)
{
char *buf, *str = NULL;
int size = 256;
int error;

*name = NULL;
*buffer = NULL;
for (;;) {
/* freed by caller */
buf = kmalloc(size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
char *str = NULL;
int error = d_namespace_path(path, buffer, &str, flags, disconnected);

error = get_name_to_buffer(path, flags, buf, size, &str, info,
disconnected);
if (error != -ENAMETOOLONG)
break;

kfree(buf);
size <<= 1;
if (size > aa_g_path_max)
return -ENAMETOOLONG;
*info = NULL;
if (info && error) {
if (error == -ENOENT)
*info = "Failed name lookup - deleted entry";
else if (error == -EACCES)
*info = "Failed name lookup - disconnected path";
else if (error == -ENAMETOOLONG)
*info = "Failed name lookup - name too long";
else
*info = "Failed name lookup";
}
*buffer = buf;

*name = str;

return error;
Expand Down

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