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DAMON fixes

PATCH In review SeongJae Park 2 participants 4 messages Nov 21, 2021 – Nov 22, 2021

Subsystems (3)
Stable branch Memory management DAMON
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SeongJae Park

author maintainer
#0 lore raw

cover DAMON fixes

This patchset is a backport of DAMON fixes that merged in the mainline, for v5.15.x stable series.

SeongJae Park (2):
mm/damon/dbgfs: use '__GFP_NOWARN' for user-specified size buffer
allocation
mm/damon/dbgfs: fix missed use of damon_dbgfs_lock

 mm/damon/dbgfs.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
Signature · 1 line
2.17.1
author maintainer
#1 lore raw

PATCH 1/2 mm/damon/dbgfs: use '__GFP_NOWARN' for user-specified size buffer allocation

commit db7a347b26fe05d2e8c115bb24dfd908d0252bc3 upstream.

Patch series "DAMON fixes".

This patch (of 2):

DAMON users can trigger below warning in '__alloc_pages()' by invoking write() to some DAMON debugfs files with arbitrarily high count argument, because DAMON debugfs interface allocates some buffers based on the user-specified 'count'.

        if (unlikely(order >= MAX_ORDER)) {
                WARN_ON_ONCE(!(gfp & __GFP_NOWARN));
                return NULL;
        }

Because the DAMON debugfs interface code checks failure of the 'kmalloc()', this commit simply suppresses the warnings by adding '__GFP_NOWARN' flag.

Link https://lkml.kernel.org/r/[email protected] open here
Link https://lkml.kernel.org/r/[email protected] open here
Fixes 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by SeongJae Park <[email protected]>
Cc <[email protected]> # 5.15.x
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
---
 mm/damon/dbgfs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
mm/damon/dbgfs.c +2 -2
index faee070977d8..2741ff79e8e8 100644
@@ -32,7 +32,7 @@ static char *user_input_str(const char __user *buf, size_t count, loff_t *ppos)
 	if (*ppos)
 		return ERR_PTR(-EINVAL);
 
-	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	kbuf = kmalloc(count + 1, GFP_KERNEL | __GFP_NOWARN);
 	if (!kbuf)
 		return ERR_PTR(-ENOMEM);
 

@@ -247,7 +247,7 @@ static ssize_t dbgfs_kdamond_pid_read(struct file *file,
 	char *kbuf;
 	ssize_t len;
 
-	kbuf = kmalloc(count, GFP_KERNEL);
+	kbuf = kmalloc(count, GFP_KERNEL | __GFP_NOWARN);
 	if (!kbuf)
 		return -ENOMEM;
Signature · 1 line
2.17.1
author maintainer
#2 lore raw

PATCH 2/2 mm/damon/dbgfs: fix missed use of damon_dbgfs_lock

In reply to SeongJae Park

commit d78f3853f831eee46c6dbe726debf3be9e9c0d05 upstream.

DAMON debugfs is supposed to protect dbgfs_ctxs, dbgfs_nr_ctxs, and dbgfs_dirs using damon_dbgfs_lock. However, some of the code is accessing the variables without the protection. This fixes it by protecting all such accesses.

Link https://lkml.kernel.org/r/[email protected] open here
Fixes 75c1c2b53c78 ("mm/damon/dbgfs: support multiple contexts")
Signed-off-by SeongJae Park <[email protected]>
Cc <[email protected]> # 5.15.x
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
---
 mm/damon/dbgfs.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
mm/damon/dbgfs.c +8 -3
index 2741ff79e8e8..f94d19a690df 100644
@@ -538,12 +538,14 @@ static ssize_t dbgfs_monitor_on_write(struct file *file,
 		return -EINVAL;
 	}
 
+	mutex_lock(&damon_dbgfs_lock);
 	if (!strncmp(kbuf, "on", count))
 		err = damon_start(dbgfs_ctxs, dbgfs_nr_ctxs);
 	else if (!strncmp(kbuf, "off", count))
 		err = damon_stop(dbgfs_ctxs, dbgfs_nr_ctxs);
 	else
 		err = -EINVAL;
+	mutex_unlock(&damon_dbgfs_lock);
 
 	if (err)
 		ret = err;

@@ -596,15 +598,16 @@ static int __init __damon_dbgfs_init(void)
 
 static int __init damon_dbgfs_init(void)
 {
-	int rc;
+	int rc = -ENOMEM;
 
+	mutex_lock(&damon_dbgfs_lock);
 	dbgfs_ctxs = kmalloc(sizeof(*dbgfs_ctxs), GFP_KERNEL);
 	if (!dbgfs_ctxs)
-		return -ENOMEM;
+		goto out;
 	dbgfs_ctxs[0] = dbgfs_new_ctx();
 	if (!dbgfs_ctxs[0]) {
 		kfree(dbgfs_ctxs);
-		return -ENOMEM;
+		goto out;
 	}
 	dbgfs_nr_ctxs = 1;
 

@@ -615,6 +618,8 @@ static int __init damon_dbgfs_init(void)
 		pr_err("%s: dbgfs init failed\n", __func__);
 	}
 
+out:
+	mutex_unlock(&damon_dbgfs_lock);
 	return rc;
 }
Signature · 1 line
2.17.1
maintainer
#3 lore raw
In reply to SeongJae Park
Quoted 14 lines · SeongJae Park

This patchset is a backport of DAMON fixes that merged in the mainline, for v5.15.x stable series.

SeongJae Park (2):
mm/damon/dbgfs: use '__GFP_NOWARN' for user-specified size buffer
allocation
mm/damon/dbgfs: fix missed use of damon_dbgfs_lock

 mm/damon/dbgfs.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
Signature · 1 line
2.17.1

Now queued up, thanks for the backports.

greg k-h