In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
cifs: Fix busy dentry used after unmounting<\/p>\n
Since commit 340cea84f691c (“cifs: open files should not hold ref on
\nsuperblock”), cifs file only holds the dentry ref_cnt, the cifs file
\nclose work(cfile->deferred) could be executed after unmounting, which
\nwill trigger a warning in generic_shutdown_super:
\n BUG: Dentry 00000000a14a6845{i=c,n=file} still in use (1) [unmount of
\n cifs cifs]<\/p>\n
The detailed processs is:
\n process A process B kworker
\n fd = open(PATH)
\n vfs_open
\n file->__f_path = *path \/\/ dentry->d_lockref.count = 1
\n cifs_open
\n cifs_new_fileinfo
\n cfile->dentry = dget(dentry) \/\/ dentry->d_lockref.count = 2
\n close(fd)
\n __fput
\n cifs_close
\n queue_delayed_work(deferredclose_wq, cfile->deferred)
\n dput(dentry) \/\/ dentry->d_lockref.count = 1
\n\t\t\t smb2_deferred_work_close
\n\t\t\t\t\t _cifsFileInfo_put
\n\t\t\t\t\t list_del(&cifs_file->flist)
\n umount
\n\t\t cleanup_mnt
\n\t\t deactivate_super
\n\t\t cifs_kill_sb
\n\t\t cifs_close_all_deferred_files_sb
\n\t\t\t cifs_close_all_deferred_files
\n\t\t\t \/\/ cannot find cfile, skip _cifsFileInfo_put
\n\t\t\tkill_anon_super
\n\t\t\t generic_shutdown_super
\n\t\t\t shrink_dcache_for_umount
\n\t\t\t umount_check
\n\t\t\t WARN ! \/\/ dentry->d_lockref.count = 1
\n\t\t\t\t\t cifsFileInfo_put_final
\n\t\t\t\t\t dput(cifs_file->dentry)
\n\t\t \/\/ dentry->d_lockref.count = 0<\/p>\n
Fix it by flushing ‘deferredclose_wq’ before calling kill_anon_super.<\/p>\n
Fetch a reproducer in https:\/\/bugzilla.kernel.org\/show_bug.cgi?id=221548.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
cifs: Fix busy dentry used after unmounting<\/p>\n
Since commit 340cea84f691c (“cifs: open files should not hold ref on
\nsuperblock”), cif<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-15078","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/15078","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15078"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15078"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15078"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}