Patch "mount: handle OOM on mnt_warn_timestamp_expiry" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    mount: handle OOM on mnt_warn_timestamp_expiry

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mount-handle-oom-on-mnt_warn_timestamp_expiry.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1bccc6423b460e6bd38a953051ccc95b6a56a1b1
Author: Olaf Hering <olaf@xxxxxxxxx>
Date:   Tue Jul 30 10:58:13 2024 +0200

    mount: handle OOM on mnt_warn_timestamp_expiry
    
    [ Upstream commit 4bcda1eaf184e308f07f9c61d3a535f9ce477ce8 ]
    
    If no page could be allocated, an error pointer was used as format
    string in pr_warn.
    
    Rearrange the code to return early in case of OOM. Also add a check
    for the return value of d_path.
    
    Fixes: f8b92ba67c5d ("mount: Add mount warning for impending timestamp expiry")
    Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20240730085856.32385-1-olaf@xxxxxxxxx
    [brauner: rewrite commit and commit message]
    Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/namespace.c b/fs/namespace.c
index f1c0e0a705621..281f08eaba5b9 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2494,8 +2494,15 @@ static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *
 	if (!__mnt_is_readonly(mnt) &&
 	   (!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) &&
 	   (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
-		char *buf = (char *)__get_free_page(GFP_KERNEL);
-		char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
+		char *buf, *mntpath;
+
+		buf = (char *)__get_free_page(GFP_KERNEL);
+		if (buf)
+			mntpath = d_path(mountpoint, buf, PAGE_SIZE);
+		else
+			mntpath = ERR_PTR(-ENOMEM);
+		if (IS_ERR(mntpath))
+			mntpath = "(unknown)";
 
 		pr_warn("%s filesystem being %s at %s supports timestamps until %ptTd (0x%llx)\n",
 			sb->s_type->name,
@@ -2503,8 +2510,9 @@ static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *
 			mntpath, &sb->s_time_max,
 			(unsigned long long)sb->s_time_max);
 
-		free_page((unsigned long)buf);
 		sb->s_iflags |= SB_I_TS_EXPIRY_WARNED;
+		if (buf)
+			free_page((unsigned long)buf);
 	}
 }