[PATCH] mm/shmem.c: check the return value of mpol_to_str()

[Chen Gang <gang.chen@xxxxxxxxxxx>]

mpol_to_str() may fail, and not fill the buffer (e.g. -EINVAL), so need
check about it, or buffer may not be zero based, and next seq_printf()
will cause issue.

Also need let shmem_show_mpol() return value, since it may fail.

Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
Reviewed-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
---
 mm/shmem.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index f00c1c1..b4d44db 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -883,16 +883,20 @@ redirty:
 
 #ifdef CONFIG_NUMA
 #ifdef CONFIG_TMPFS
-static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
+static int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 {
 	char buffer[64];
+	int ret;
 
 	if (!mpol || mpol->mode == MPOL_DEFAULT)
-		return;		/* show nothing */
+		return 0;		/* show nothing */
 
-	mpol_to_str(buffer, sizeof(buffer), mpol);
+	ret = mpol_to_str(buffer, sizeof(buffer), mpol);
+	if (ret < 0)
+		return ret;
 
 	seq_printf(seq, ",mpol=%s", buffer);
+	return 0;
 }
 
 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
@@ -951,8 +955,9 @@ static struct page *shmem_alloc_page(gfp_t gfp,
 }
 #else /* !CONFIG_NUMA */
 #ifdef CONFIG_TMPFS
-static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
+static inline int shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 {
+	return 0;
 }
 #endif /* CONFIG_TMPFS */
 
@@ -2555,8 +2560,7 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
 	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
 		seq_printf(seq, ",gid=%u",
 				from_kgid_munged(&init_user_ns, sbinfo->gid));
-	shmem_show_mpol(seq, sbinfo->mpol);
-	return 0;
+	return shmem_show_mpol(seq, sbinfo->mpol);
 }
 #endif /* CONFIG_TMPFS */
 
-- 
1.7.7.6

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