[PATCH 5.15 105/691] mount: handle OOM on mnt_warn_timestamp_expiry

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5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Olaf Hering <olaf@xxxxxxxxx>

[ 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>
---
 fs/namespace.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index c17e3a6ebd179..22af4b6c737f4 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2569,8 +2569,15 @@ 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,
@@ -2578,8 +2585,9 @@ 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);
 	}
 }
 
-- 
2.43.0







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