From df4565f9ebdc4d6dc50edc6e8fed08004e328332 Mon Sep 17 00:00:00 2001 From: Nicolai Stange Date: Tue, 24 May 2016 14:05:05 +0200 Subject: [PATCH] kernel/kcov: unproxify debugfs file's fops Since commit 49d200deaa68 ("debugfs: prevent access to removed files' private data"), a debugfs file's file_operations methods get proxied through lifetime aware wrappers. However, only a certain subset of the file_operations members is supported by debugfs and ->mmap isn't among them -- it appears to be NULL from the VFS layer's perspective. This behaviour breaks the /sys/kernel/debug/kcov file introduced concurrently with commit 5c9a8750a640 ("kernel: add kcov code coverage"). Since that file never gets removed, there is no file removal race and thus, a lifetime checking proxy isn't needed. Avoid the proxying for /sys/kernel/debug/kcov by creating it via debugfs_create_file_unsafe() rather than debugfs_create_file(). Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data") Fixes: 5c9a8750a640 ("kernel: add kcov code coverage") Reported-by: Sasha Levin Signed-off-by: Nicolai Stange Signed-off-by: Greg Kroah-Hartman --- kernel/kcov.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/kcov.c b/kernel/kcov.c index a02f2dddd1d7..8d44b3fea9d0 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -264,7 +264,12 @@ static const struct file_operations kcov_fops = { static int __init kcov_init(void) { - if (!debugfs_create_file("kcov", 0600, NULL, NULL, &kcov_fops)) { + /* + * The kcov debugfs file won't ever get removed and thus, + * there is no need to protect it against removal races. The + * use of debugfs_create_file_unsafe() is actually safe here. + */ + if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) { pr_err("failed to create kcov in debugfs\n"); return -ENOMEM; } -- 2.20.1