[PATCH 3.14 34/43] cifs: fix use-after-free bug in find_writable_file
3.14-stable review patch. If anyone has any objections, please let me know. -- From: David Disseldorp commit e1e9bda22d7ddf88515e8fe401887e313922823e upstream. Under intermittent network outages, find_writable_file() is susceptible to the following race condition, which results in a user-after-free in the cifs_writepages code-path: Thread 1Thread 2 inv_file = NULL refind = 0 spin_lock(_file_list_lock) // invalidHandle found on openFileList inv_file = open_file // inv_file->count currently 1 cifsFileInfo_get(inv_file) // inv_file->count = 2 spin_unlock(_file_list_lock); cifs_reopen_file()cifs_close() // fails (rc != 0)->cifsFileInfo_put() spin_lock(_file_list_lock) // inv_file->count = 1 spin_unlock(_file_list_lock) spin_lock(_file_list_lock); list_move_tail(_file->flist, _inode->openFileList); spin_unlock(_file_list_lock); cifsFileInfo_put(inv_file); ->spin_lock(_file_list_lock) // inv_file->count = 0 list_del(_file->flist); // cleanup!! kfree(cifs_file); spin_unlock(_file_list_lock); spin_lock(_file_list_lock); ++refind; // refind = 1 goto refind_writable; At this point we loop back through with an invalid inv_file pointer and a refind value of 1. On second pass, inv_file is not overwritten on openFileList traversal, and is subsequently dereferenced. Signed-off-by: David Disseldorp Reviewed-by: Jeff Layton Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/cifs/file.c |1 + 1 file changed, 1 insertion(+) --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -1821,6 +1821,7 @@ refind_writable: cifsFileInfo_put(inv_file); spin_lock(_file_list_lock); ++refind; + inv_file = NULL; goto refind_writable; } } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 3.14 34/43] cifs: fix use-after-free bug in find_writable_file
3.14-stable review patch. If anyone has any objections, please let me know. -- From: David Disseldorp dd...@suse.de commit e1e9bda22d7ddf88515e8fe401887e313922823e upstream. Under intermittent network outages, find_writable_file() is susceptible to the following race condition, which results in a user-after-free in the cifs_writepages code-path: Thread 1Thread 2 inv_file = NULL refind = 0 spin_lock(cifs_file_list_lock) // invalidHandle found on openFileList inv_file = open_file // inv_file-count currently 1 cifsFileInfo_get(inv_file) // inv_file-count = 2 spin_unlock(cifs_file_list_lock); cifs_reopen_file()cifs_close() // fails (rc != 0)-cifsFileInfo_put() spin_lock(cifs_file_list_lock) // inv_file-count = 1 spin_unlock(cifs_file_list_lock) spin_lock(cifs_file_list_lock); list_move_tail(inv_file-flist, cifs_inode-openFileList); spin_unlock(cifs_file_list_lock); cifsFileInfo_put(inv_file); -spin_lock(cifs_file_list_lock) // inv_file-count = 0 list_del(cifs_file-flist); // cleanup!! kfree(cifs_file); spin_unlock(cifs_file_list_lock); spin_lock(cifs_file_list_lock); ++refind; // refind = 1 goto refind_writable; At this point we loop back through with an invalid inv_file pointer and a refind value of 1. On second pass, inv_file is not overwritten on openFileList traversal, and is subsequently dereferenced. Signed-off-by: David Disseldorp dd...@suse.de Reviewed-by: Jeff Layton jlay...@samba.org Signed-off-by: Steve French smfre...@gmail.com Signed-off-by: Greg Kroah-Hartman gre...@linuxfoundation.org --- fs/cifs/file.c |1 + 1 file changed, 1 insertion(+) --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -1821,6 +1821,7 @@ refind_writable: cifsFileInfo_put(inv_file); spin_lock(cifs_file_list_lock); ++refind; + inv_file = NULL; goto refind_writable; } } -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
