Commit eb143f87 authored by Martin Fuzzey's avatar Martin Fuzzey Committed by Greg Kroah-Hartman
Browse files

binder: fix log spam for existing debugfs file creation. 



Since commit 43e23b6c ("debugfs: log errors when something goes wrong")
debugfs logs attempts to create existing files.

However binder attempts to create multiple debugfs files with
the same name when a single PID has multiple contexts, this leads
to log spamming during an Android boot (17 such messages during
boot on my system).

Fix this by checking if we already know the PID and only create
the debugfs entry for the first context per PID.

Do the same thing for binderfs for symmetry.

Signed-off-by: default avatarMartin Fuzzey <martin.fuzzey@flowbird.group>
Acked-by: default avatarTodd Kjos <tkjos@google.com>
Fixes: 43e23b6c ("debugfs: log errors when something goes wrong")
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1578671054-5982-1-git-send-email-martin.fuzzey@flowbird.group


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 10d3e38c

drivers/android/binder.c

+19 −18
Original line number Diff line number Diff line
@@ -5199,10 +5199,11 @@ err_bad_arg: 


static int binder_open(struct inode *nodp, struct file *filp)

{

	struct binder_proc *proc;

	struct binder_proc *proc, *itr;

	struct binder_device *binder_dev;

	struct binderfs_info *info;

	struct dentry *binder_binderfs_dir_entry_proc = NULL;

	bool existing_pid = false;



	binder_debug(BINDER_DEBUG_OPEN_CLOSE, "%s: %d:%d\n", __func__,

		     current->group_leader->pid, current->pid);
@@ -5235,19 +5236,24 @@ static int binder_open(struct inode *nodp, struct file *filp) 
	filp->private_data = proc;



	mutex_lock(&binder_procs_lock);

	hlist_for_each_entry(itr, &binder_procs, proc_node) {

		if (itr->pid == proc->pid) {

			existing_pid = true;

			break;

		}

	}

	hlist_add_head(&proc->proc_node, &binder_procs);

	mutex_unlock(&binder_procs_lock);



	if (binder_debugfs_dir_entry_proc) {

	if (binder_debugfs_dir_entry_proc && !existing_pid) {

		char strbuf[11];



		snprintf(strbuf, sizeof(strbuf), "%u", proc->pid);

		/*

		 * proc debug entries are shared between contexts, so

		 * this will fail if the process tries to open the driver

		 * again with a different context. The priting code will

		 * anyway print all contexts that a given PID has, so this

		 * is not a problem.

		 * proc debug entries are shared between contexts.

		 * Only create for the first PID to avoid debugfs log spamming

		 * The printing code will anyway print all contexts for a given

		 * PID so this is not a problem.

		 */

		proc->debugfs_entry = debugfs_create_file(strbuf, 0444,

			binder_debugfs_dir_entry_proc,
@@ -5255,19 +5261,16 @@ static int binder_open(struct inode *nodp, struct file *filp) 
			&proc_fops);

	}



	if (binder_binderfs_dir_entry_proc) {

	if (binder_binderfs_dir_entry_proc && !existing_pid) {

		char strbuf[11];

		struct dentry *binderfs_entry;



		snprintf(strbuf, sizeof(strbuf), "%u", proc->pid);

		/*

		 * Similar to debugfs, the process specific log file is shared

		 * between contexts. If the file has already been created for a

		 * process, the following binderfs_create_file() call will

		 * fail with error code EEXIST if another context of the same

		 * process invoked binder_open(). This is ok since same as

		 * debugfs, the log file will contain information on all

		 * contexts of a given PID.

		 * between contexts. Only create for the first PID.

		 * This is ok since same as debugfs, the log file will contain

		 * information on all contexts of a given PID.

		 */

		binderfs_entry = binderfs_create_file(binder_binderfs_dir_entry_proc,

			strbuf, &proc_fops, (void *)(unsigned long)proc->pid);
@@ -5277,12 +5280,10 @@ static int binder_open(struct inode *nodp, struct file *filp) 
			int error;



			error = PTR_ERR(binderfs_entry);

			if (error != -EEXIST) {

			pr_warn("Unable to create file %s in binderfs (error %d)\n",

				strbuf, error);

		}

	}

	}



	return 0;

}

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