| Message ID | 20190730015729.4406-1-miles.chen@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] mm: memcontrol: fix use after free in mem_cgroup_iter() | expand |
[Cc Andrew to pick up the patch] On Tue 30-07-19 09:57:29, Miles Chen wrote: > This patch is sent to report an use after free in mem_cgroup_iter() > after merging commit: be2657752e9e "mm: memcg: fix use after free in > mem_cgroup_iter()". > > I work with android kernel tree (4.9 & 4.14), and the commit: > be2657752e9e "mm: memcg: fix use after free in mem_cgroup_iter()" has > been merged to the trees. However, I can still observe use after free > issues addressed in the commit be2657752e9e. > (on low-end devices, a few times this month) > > backtrace: > css_tryget <- crash here > mem_cgroup_iter > shrink_node > shrink_zones > do_try_to_free_pages > try_to_free_pages > __perform_reclaim > __alloc_pages_direct_reclaim > __alloc_pages_slowpath > __alloc_pages_nodemask > > To debug, I poisoned mem_cgroup before freeing it: > > static void __mem_cgroup_free(struct mem_cgroup *memcg) > for_each_node(node) > free_mem_cgroup_per_node_info(memcg, node); > free_percpu(memcg->stat); > + /* poison memcg before freeing it */ > + memset(memcg, 0x78, sizeof(struct mem_cgroup)); > kfree(memcg); > } > > The coredump shows the position=0xdbbc2a00 is freed. > > (gdb) p/x ((struct mem_cgroup_per_node *)0xe5009e00)->iter[8] > $13 = {position = 0xdbbc2a00, generation = 0x2efd} > > 0xdbbc2a00: 0xdbbc2e00 0x00000000 0xdbbc2800 0x00000100 > 0xdbbc2a10: 0x00000200 0x78787878 0x00026218 0x00000000 > 0xdbbc2a20: 0xdcad6000 0x00000001 0x78787800 0x00000000 > 0xdbbc2a30: 0x78780000 0x00000000 0x0068fb84 0x78787878 > 0xdbbc2a40: 0x78787878 0x78787878 0x78787878 0xe3fa5cc0 > 0xdbbc2a50: 0x78787878 0x78787878 0x00000000 0x00000000 > 0xdbbc2a60: 0x00000000 0x00000000 0x00000000 0x00000000 > 0xdbbc2a70: 0x00000000 0x00000000 0x00000000 0x00000000 > 0xdbbc2a80: 0x00000000 0x00000000 0x00000000 0x00000000 > 0xdbbc2a90: 0x00000001 0x00000000 0x00000000 0x00100000 > 0xdbbc2aa0: 0x00000001 0xdbbc2ac8 0x00000000 0x00000000 > 0xdbbc2ab0: 0x00000000 0x00000000 0x00000000 0x00000000 > 0xdbbc2ac0: 0x00000000 0x00000000 0xe5b02618 0x00001000 > 0xdbbc2ad0: 0x00000000 0x78787878 0x78787878 0x78787878 > 0xdbbc2ae0: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2af0: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b00: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b10: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b20: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b30: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b40: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b50: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b60: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b70: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2b80: 0x78787878 0x78787878 0x00000000 0x78787878 > 0xdbbc2b90: 0x78787878 0x78787878 0x78787878 0x78787878 > 0xdbbc2ba0: 0x78787878 0x78787878 0x78787878 0x78787878 > > In the reclaim path, try_to_free_pages() does not setup > sc.target_mem_cgroup and sc is passed to do_try_to_free_pages(), ..., > shrink_node(). > > In mem_cgroup_iter(), root is set to root_mem_cgroup because > sc->target_mem_cgroup is NULL. > It is possible to assign a memcg to root_mem_cgroup.nodeinfo.iter in > mem_cgroup_iter(). > > try_to_free_pages > struct scan_control sc = {...}, target_mem_cgroup is 0x0; > do_try_to_free_pages > shrink_zones > shrink_node > mem_cgroup *root = sc->target_mem_cgroup; > memcg = mem_cgroup_iter(root, NULL, &reclaim); > mem_cgroup_iter() > if (!root) > root = root_mem_cgroup; > ... > > css = css_next_descendant_pre(css, &root->css); > memcg = mem_cgroup_from_css(css); > cmpxchg(&iter->position, pos, memcg); > > My device uses memcg non-hierarchical mode. > When we release a memcg: invalidate_reclaim_iterators() reaches only > dead_memcg and its parents. If non-hierarchical mode is used, > invalidate_reclaim_iterators() never reaches root_mem_cgroup. > > static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) > { > struct mem_cgroup *memcg = dead_memcg; > > for (; memcg; memcg = parent_mem_cgroup(memcg) > ... > } > > So the use after free scenario looks like: > > CPU1 CPU2 > > try_to_free_pages > do_try_to_free_pages > shrink_zones > shrink_node > mem_cgroup_iter() > if (!root) > root = root_mem_cgroup; > ... > css = css_next_descendant_pre(css, &root->css); > memcg = mem_cgroup_from_css(css); > cmpxchg(&iter->position, pos, memcg); > > invalidate_reclaim_iterators(memcg); > ... > __mem_cgroup_free() > kfree(memcg); > > try_to_free_pages > do_try_to_free_pages > shrink_zones > shrink_node > mem_cgroup_iter() > if (!root) > root = root_mem_cgroup; > ... > mz = mem_cgroup_nodeinfo(root, reclaim->pgdat->node_id); > iter = &mz->iter[reclaim->priority]; > pos = READ_ONCE(iter->position); > css_tryget(&pos->css) <- use after free > > To avoid this, we should also invalidate root_mem_cgroup.nodeinfo.iter in > invalidate_reclaim_iterators(). > > Change since v1: > Add a comment to explain why we need to handle root_mem_cgroup separately. > Rename invalid_root to invalidate_root. > > Change since v2: > Add fix tag > > Change since v3: > Remove confusing 'invalidate_root', make the code easier to read > > Fixes: 5ac8fb31ad2e ("mm: memcontrol: convert reclaim iterator to simple css refcounting") > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Michal Hocko <mhocko@kernel.org> > Signed-off-by: Miles Chen <miles.chen@mediatek.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memcontrol.c | 39 +++++++++++++++++++++++++++++---------- > 1 file changed, 29 insertions(+), 10 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index cdbb7a84cb6e..8a2a2d5cfc26 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1130,26 +1130,45 @@ void mem_cgroup_iter_break(struct mem_cgroup *root, > css_put(&prev->css); > } > > -static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) > +static void __invalidate_reclaim_iterators(struct mem_cgroup *from, > + struct mem_cgroup *dead_memcg) > { > - struct mem_cgroup *memcg = dead_memcg; > struct mem_cgroup_reclaim_iter *iter; > struct mem_cgroup_per_node *mz; > int nid; > int i; > > - for (; memcg; memcg = parent_mem_cgroup(memcg)) { > - for_each_node(nid) { > - mz = mem_cgroup_nodeinfo(memcg, nid); > - for (i = 0; i <= DEF_PRIORITY; i++) { > - iter = &mz->iter[i]; > - cmpxchg(&iter->position, > - dead_memcg, NULL); > - } > + for_each_node(nid) { > + mz = mem_cgroup_nodeinfo(from, nid); > + for (i = 0; i <= DEF_PRIORITY; i++) { > + iter = &mz->iter[i]; > + cmpxchg(&iter->position, > + dead_memcg, NULL); > } > } > } > > +static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) > +{ > + struct mem_cgroup *memcg = dead_memcg; > + struct mem_cgroup *last; > + > + do { > + __invalidate_reclaim_iterators(memcg, dead_memcg); > + last = memcg; > + } while (memcg = parent_mem_cgroup(memcg)); > + > + /* > + * When cgruop1 non-hierarchy mode is used, > + * parent_mem_cgroup() does not walk all the way up to the > + * cgroup root (root_mem_cgroup). So we have to handle > + * dead_memcg from cgroup root separately. > + */ > + if (last != root_mem_cgroup) > + __invalidate_reclaim_iterators(root_mem_cgroup, > + dead_memcg); > +} > + > /** > * mem_cgroup_scan_tasks - iterate over tasks of a memory cgroup hierarchy > * @memcg: hierarchy root > -- > 2.18.0
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index cdbb7a84cb6e..8a2a2d5cfc26 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1130,26 +1130,45 @@ void mem_cgroup_iter_break(struct mem_cgroup *root, css_put(&prev->css); } -static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) +static void __invalidate_reclaim_iterators(struct mem_cgroup *from, + struct mem_cgroup *dead_memcg) { - struct mem_cgroup *memcg = dead_memcg; struct mem_cgroup_reclaim_iter *iter; struct mem_cgroup_per_node *mz; int nid; int i; - for (; memcg; memcg = parent_mem_cgroup(memcg)) { - for_each_node(nid) { - mz = mem_cgroup_nodeinfo(memcg, nid); - for (i = 0; i <= DEF_PRIORITY; i++) { - iter = &mz->iter[i]; - cmpxchg(&iter->position, - dead_memcg, NULL); - } + for_each_node(nid) { + mz = mem_cgroup_nodeinfo(from, nid); + for (i = 0; i <= DEF_PRIORITY; i++) { + iter = &mz->iter[i]; + cmpxchg(&iter->position, + dead_memcg, NULL); } } } +static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) +{ + struct mem_cgroup *memcg = dead_memcg; + struct mem_cgroup *last; + + do { + __invalidate_reclaim_iterators(memcg, dead_memcg); + last = memcg; + } while (memcg = parent_mem_cgroup(memcg)); + + /* + * When cgruop1 non-hierarchy mode is used, + * parent_mem_cgroup() does not walk all the way up to the + * cgroup root (root_mem_cgroup). So we have to handle + * dead_memcg from cgroup root separately. + */ + if (last != root_mem_cgroup) + __invalidate_reclaim_iterators(root_mem_cgroup, + dead_memcg); +} + /** * mem_cgroup_scan_tasks - iterate over tasks of a memory cgroup hierarchy * @memcg: hierarchy root
This patch is sent to report an use after free in mem_cgroup_iter() after merging commit: be2657752e9e "mm: memcg: fix use after free in mem_cgroup_iter()". I work with android kernel tree (4.9 & 4.14), and the commit: be2657752e9e "mm: memcg: fix use after free in mem_cgroup_iter()" has been merged to the trees. However, I can still observe use after free issues addressed in the commit be2657752e9e. (on low-end devices, a few times this month) backtrace: css_tryget <- crash here mem_cgroup_iter shrink_node shrink_zones do_try_to_free_pages try_to_free_pages __perform_reclaim __alloc_pages_direct_reclaim __alloc_pages_slowpath __alloc_pages_nodemask To debug, I poisoned mem_cgroup before freeing it: static void __mem_cgroup_free(struct mem_cgroup *memcg) for_each_node(node) free_mem_cgroup_per_node_info(memcg, node); free_percpu(memcg->stat); + /* poison memcg before freeing it */ + memset(memcg, 0x78, sizeof(struct mem_cgroup)); kfree(memcg); } The coredump shows the position=0xdbbc2a00 is freed. (gdb) p/x ((struct mem_cgroup_per_node *)0xe5009e00)->iter[8] $13 = {position = 0xdbbc2a00, generation = 0x2efd} 0xdbbc2a00: 0xdbbc2e00 0x00000000 0xdbbc2800 0x00000100 0xdbbc2a10: 0x00000200 0x78787878 0x00026218 0x00000000 0xdbbc2a20: 0xdcad6000 0x00000001 0x78787800 0x00000000 0xdbbc2a30: 0x78780000 0x00000000 0x0068fb84 0x78787878 0xdbbc2a40: 0x78787878 0x78787878 0x78787878 0xe3fa5cc0 0xdbbc2a50: 0x78787878 0x78787878 0x00000000 0x00000000 0xdbbc2a60: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2a70: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2a80: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2a90: 0x00000001 0x00000000 0x00000000 0x00100000 0xdbbc2aa0: 0x00000001 0xdbbc2ac8 0x00000000 0x00000000 0xdbbc2ab0: 0x00000000 0x00000000 0x00000000 0x00000000 0xdbbc2ac0: 0x00000000 0x00000000 0xe5b02618 0x00001000 0xdbbc2ad0: 0x00000000 0x78787878 0x78787878 0x78787878 0xdbbc2ae0: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2af0: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b00: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b10: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b20: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b30: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b40: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b50: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b60: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b70: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2b80: 0x78787878 0x78787878 0x00000000 0x78787878 0xdbbc2b90: 0x78787878 0x78787878 0x78787878 0x78787878 0xdbbc2ba0: 0x78787878 0x78787878 0x78787878 0x78787878 In the reclaim path, try_to_free_pages() does not setup sc.target_mem_cgroup and sc is passed to do_try_to_free_pages(), ..., shrink_node(). In mem_cgroup_iter(), root is set to root_mem_cgroup because sc->target_mem_cgroup is NULL. It is possible to assign a memcg to root_mem_cgroup.nodeinfo.iter in mem_cgroup_iter(). try_to_free_pages struct scan_control sc = {...}, target_mem_cgroup is 0x0; do_try_to_free_pages shrink_zones shrink_node mem_cgroup *root = sc->target_mem_cgroup; memcg = mem_cgroup_iter(root, NULL, &reclaim); mem_cgroup_iter() if (!root) root = root_mem_cgroup; ... css = css_next_descendant_pre(css, &root->css); memcg = mem_cgroup_from_css(css); cmpxchg(&iter->position, pos, memcg); My device uses memcg non-hierarchical mode. When we release a memcg: invalidate_reclaim_iterators() reaches only dead_memcg and its parents. If non-hierarchical mode is used, invalidate_reclaim_iterators() never reaches root_mem_cgroup. static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) { struct mem_cgroup *memcg = dead_memcg; for (; memcg; memcg = parent_mem_cgroup(memcg) ... } So the use after free scenario looks like: CPU1 CPU2 try_to_free_pages do_try_to_free_pages shrink_zones shrink_node mem_cgroup_iter() if (!root) root = root_mem_cgroup; ... css = css_next_descendant_pre(css, &root->css); memcg = mem_cgroup_from_css(css); cmpxchg(&iter->position, pos, memcg); invalidate_reclaim_iterators(memcg); ... __mem_cgroup_free() kfree(memcg); try_to_free_pages do_try_to_free_pages shrink_zones shrink_node mem_cgroup_iter() if (!root) root = root_mem_cgroup; ... mz = mem_cgroup_nodeinfo(root, reclaim->pgdat->node_id); iter = &mz->iter[reclaim->priority]; pos = READ_ONCE(iter->position); css_tryget(&pos->css) <- use after free To avoid this, we should also invalidate root_mem_cgroup.nodeinfo.iter in invalidate_reclaim_iterators(). Change since v1: Add a comment to explain why we need to handle root_mem_cgroup separately. Rename invalid_root to invalidate_root. Change since v2: Add fix tag Change since v3: Remove confusing 'invalidate_root', make the code easier to read Fixes: 5ac8fb31ad2e ("mm: memcontrol: convert reclaim iterator to simple css refcounting") Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Miles Chen <miles.chen@mediatek.com> --- mm/memcontrol.c | 39 +++++++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 10 deletions(-)