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authorTejun Heo <tj@kernel.org>2022-12-08 05:53:15 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-12-14 13:28:27 +0300
commite1ae97624ecf400ea56c238bff23e5cd139df0b8 (patch)
tree47b5585a46d9418d84cc4352d06ab3e18ce070b3 /include
parent2572ab14b73aa45b6ae7e4c089ccf119fed5cf89 (diff)
downloadlinux-e1ae97624ecf400ea56c238bff23e5cd139df0b8.tar.xz
memcg: fix possible use-after-free in memcg_write_event_control()
commit 4a7ba45b1a435e7097ca0f79a847d0949d0eb088 upstream. memcg_write_event_control() accesses the dentry->d_name of the specified control fd to route the write call. As a cgroup interface file can't be renamed, it's safe to access d_name as long as the specified file is a regular cgroup file. Also, as these cgroup interface files can't be removed before the directory, it's safe to access the parent too. Prior to 347c4a874710 ("memcg: remove cgroup_event->cft"), there was a call to __file_cft() which verified that the specified file is a regular cgroupfs file before further accesses. The cftype pointer returned from __file_cft() was no longer necessary and the commit inadvertently dropped the file type check with it allowing any file to slip through. With the invarients broken, the d_name and parent accesses can now race against renames and removals of arbitrary files and cause use-after-free's. Fix the bug by resurrecting the file type check in __file_cft(). Now that cgroupfs is implemented through kernfs, checking the file operations needs to go through a layer of indirection. Instead, let's check the superblock and dentry type. Link: https://lkml.kernel.org/r/Y5FRm/cfcKPGzWwl@slm.duckdns.org Fixes: 347c4a874710 ("memcg: remove cgroup_event->cft") Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jann Horn <jannh@google.com> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: <stable@vger.kernel.org> [3.14+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/cgroup.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 02da4e1def61..6b5d35f5087c 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -69,6 +69,7 @@ struct css_task_iter {
struct list_head iters_node; /* css_set->task_iters */
};
+extern struct file_system_type cgroup_fs_type;
extern struct cgroup_root cgrp_dfl_root;
extern struct css_set init_css_set;