Commit 3edf652f authored by Eric W. Biederman's avatar Eric W. Biederman
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userns: Simplify the user and group mapping functions 



Consolidate reading the number of extents and computing the return
value in the map_id_down, map_id_range_down and map_id_range.

This removal of one read of extents makes one smp_rmb unnecessary
and makes the code safe it is executed during the map write.  Reading
the number of extents twice and depending on the result being the same
is not safe, as it could be 0 the first time and > 5 the second time,
which would lead to misinterpreting the union fields.

The consolidation of the return value just removes a duplicate
caluculation which should make it easier to understand and maintain
the code.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 11a8b927

kernel/user_namespace.c

+58 −74
Original line number Diff line number Diff line
@@ -256,28 +256,17 @@ static int cmp_map_id(const void *k, const void *e) 
 * map_id_range_down_max - Find idmap via binary search in ordered idmap array.

 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.

 */

static u32 map_id_range_down_max(struct uid_gid_map *map, u32 id, u32 count)

static struct uid_gid_extent *

map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)

{

	u32 extents;

	struct uid_gid_extent *extent;

	struct idmap_key key;



	key.map_up = false;

	key.count = count;

	key.id = id;



	extents = map->nr_extents;

	smp_rmb();



	extent = bsearch(&key, map->forward, extents,

	return bsearch(&key, map->forward, extents,

		       sizeof(struct uid_gid_extent), cmp_map_id);

	/* Map the id or note failure */

	if (extent)

		id = (id - extent->first) + extent->lower_first;

	else

		id = (u32) -1;



	return id;

}



/**
@@ -285,41 +274,43 @@ static u32 map_id_range_down_max(struct uid_gid_map *map, u32 id, u32 count) 
 * Can only be called if number of mappings is equal or less than

 * UID_GID_MAP_MAX_BASE_EXTENTS.

 */

static u32 map_id_range_down_base(struct uid_gid_map *map, u32 id, u32 count)

static struct uid_gid_extent *

map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)

{

	unsigned idx, extents;

	unsigned idx;

	u32 first, last, id2;



	id2 = id + count - 1;



	/* Find the matching extent */

	extents = map->nr_extents;

	smp_rmb();

	for (idx = 0; idx < extents; idx++) {

		first = map->extent[idx].first;

		last = first + map->extent[idx].count - 1;

		if (id >= first && id <= last &&

		    (id2 >= first && id2 <= last))

			break;

			return &map->extent[idx];

	}

	/* Map the id or note failure */

	if (idx < extents)

		id = (id - first) + map->extent[idx].lower_first;

	else

		id = (u32) -1;



	return id;

	return NULL;

}



static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)

{

	u32 extents = map->nr_extents;

	struct uid_gid_extent *extent;

	unsigned extents = map->nr_extents;

	smp_rmb();



	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)

		return map_id_range_down_base(map, id, count);

		extent = map_id_range_down_base(extents, map, id, count);

	else

		extent = map_id_range_down_max(extents, map, id, count);



	return map_id_range_down_max(map, id, count);

	/* Map the id or note failure */

	if (extent)

		id = (id - extent->first) + extent->lower_first;

	else

		id = (u32) -1;



	return id;

}



/**
@@ -327,38 +318,40 @@ static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count) 
 * Can only be called if number of mappings is equal or less than

 * UID_GID_MAP_MAX_BASE_EXTENTS.

 */

static u32 map_id_down_base(struct uid_gid_map *map, u32 id)

static struct uid_gid_extent *

map_id_down_base(unsigned extents, struct uid_gid_map *map, u32 id)

{

	unsigned idx, extents;

	unsigned idx;

	u32 first, last;



	/* Find the matching extent */

	extents = map->nr_extents;

	smp_rmb();

	for (idx = 0; idx < extents; idx++) {

		first = map->extent[idx].first;

		last = first + map->extent[idx].count - 1;

		if (id >= first && id <= last)

			break;

			return &map->extent[idx];

	}

	/* Map the id or note failure */

	if (idx < extents)

		id = (id - first) + map->extent[idx].lower_first;

	else

		id = (u32) -1;



	return id;

	return NULL;

}



static u32 map_id_down(struct uid_gid_map *map, u32 id)

{

	u32 extents = map->nr_extents;

	struct uid_gid_extent *extent;

	unsigned extents = map->nr_extents;

	smp_rmb();



	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)

		return map_id_down_base(map, id);

		extent = map_id_down_base(extents, map, id);

	else

		extent = map_id_range_down_max(extents, map, id, 1);



	/* Map the id or note failure */

	if (extent)

		id = (id - extent->first) + extent->lower_first;

	else

		id = (u32) -1;



	return map_id_range_down_max(map, id, 1);

	return id;

}



/**
@@ -366,66 +359,57 @@ static u32 map_id_down(struct uid_gid_map *map, u32 id) 
 * Can only be called if number of mappings is equal or less than

 * UID_GID_MAP_MAX_BASE_EXTENTS.

 */

static u32 map_id_up_base(struct uid_gid_map *map, u32 id)

static struct uid_gid_extent *

map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)

{

	unsigned idx, extents;

	unsigned idx;

	u32 first, last;



	/* Find the matching extent */

	extents = map->nr_extents;

	smp_rmb();

	for (idx = 0; idx < extents; idx++) {

		first = map->extent[idx].lower_first;

		last = first + map->extent[idx].count - 1;

		if (id >= first && id <= last)

			break;

			return &map->extent[idx];

	}

	/* Map the id or note failure */

	if (idx < extents)

		id = (id - first) + map->extent[idx].first;

	else

		id = (u32) -1;



	return id;

	return NULL;

}



/**

 * map_id_up_max - Find idmap via binary search in ordered idmap array.

 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.

 */

static u32 map_id_up_max(struct uid_gid_map *map, u32 id)

static struct uid_gid_extent *

map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)

{

	u32 extents;

	struct uid_gid_extent *extent;

	struct idmap_key key;



	key.map_up = true;

	key.count = 1;

	key.id = id;



	extents = map->nr_extents;

	smp_rmb();



	extent = bsearch(&key, map->reverse, extents,

	return bsearch(&key, map->reverse, extents,

		       sizeof(struct uid_gid_extent), cmp_map_id);

	/* Map the id or note failure */

	if (extent)

		id = (id - extent->lower_first) + extent->first;

	else

		id = (u32) -1;



	return id;

}



static u32 map_id_up(struct uid_gid_map *map, u32 id)

{

	u32 extents = map->nr_extents;

	struct uid_gid_extent *extent;

	unsigned extents = map->nr_extents;

	smp_rmb();



	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)

		return map_id_up_base(map, id);

		extent = map_id_up_base(extents, map, id);

	else

		extent = map_id_up_max(extents, map, id);



	return map_id_up_max(map, id);

	/* Map the id or note failure */

	if (extent)

		id = (id - extent->lower_first) + extent->first;

	else

		id = (u32) -1;



	return id;

}



/**

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