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Commit 4227c333 authored by John Johansen's avatar John Johansen
Browse files

apparmor: Move path lookup to using preallocated buffers 



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: default avatarJohn Johansen <john.johansen@canonical.com>
parent 72c8a768

security/apparmor/domain.c

+5 −3
Original line number Diff line number Diff line
@@ -357,6 +357,9 @@ 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
@@ -364,8 +367,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm) 
	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) ||
@@ -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;

}

security/apparmor/file.c

+7 −6
Original line number Diff line number Diff line
@@ -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)) {
@@ -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;

}
@@ -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;
@@ -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;

}

security/apparmor/include/path.h

+2 −2
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ enum path_flags { 
	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);

security/apparmor/path.c

+39 −75
Original line number Diff line number Diff line
@@ -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
@@ -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 */
@@ -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,

			error = disconnect(path, buf, name, flags,

					   disconnected);

		goto out;

	}



	/* resolve paths relative to chroot?*/
@@ -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)) {
@@ -146,6 +152,9 @@ 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
@@ -153,62 +162,27 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen, 
	 *    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";

	}

	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
@@ -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;