[PATCH 3/3] mm/shmem.c: check the return value of mpol_to_str()

[Chen Gang]

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 print related warning when the buffer space is not enough.


Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
---
 mm/shmem.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 75010ba..eb4eec8 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -886,11 +886,24 @@ redirty:
 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 {
 	char buffer[64];
+	int ret;
 
 	if (!mpol || mpol->mode == MPOL_DEFAULT)
 		return;		/* show nothing */
 
-	mpol_to_str(buffer, sizeof(buffer), mpol);
+	ret = mpol_to_str(buffer, sizeof(buffer), mpol);
+	if (ret < 0)
+		switch (ret) {
+		case -ENOSPC:
+			printk(KERN_WARNING
+				"in %s: string is truncated in mpol_to_str().\n",
+				__func__);
+		default:
+			printk(KERN_ERR
+				"in %s: call mpol_to_str() fail, errcode: %d. buffer: %p, size: %zu, pol: %p\n",
+				__func__, ret, buffer, sizeof(buffer), mpol);
+			return;
+		}
 
 	seq_printf(seq, ",mpol=%s", buffer);
 }
-- 
1.7.7.6
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