From: Ferdinand Blomqvist <ferdinand.blomqvist@gmail.com>
Date: Thu, 20 Jun 2019 14:10:37 +0000 (+0300)
Subject: rslib: Fix handling of of caller provided syndrome
X-Git-Tag: Ubuntu-4.15.0-61.68~710
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=f213af1c317a73008a844f6173a414b180bf202b;hp=2894ecafb808d05ad9b1f21ab3d84780930e040c;p=mirror_ubuntu-bionic-kernel.git

rslib: Fix handling of of caller provided syndrome

BugLink: https://bugs.launchpad.net/bugs/1839036

[ Upstream commit ef4d6a8556b637ad27c8c2a2cff1dda3da38e9a9 ]

Check if the syndrome provided by the caller is zero, and act
accordingly.

Signed-off-by: Ferdinand Blomqvist <ferdinand.blomqvist@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190620141039.9874-6-ferdinand.blomqvist@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
---

diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c
index 8eed0f9ac495..a5d313381539 100644
--- a/lib/reed_solomon/decode_rs.c
+++ b/lib/reed_solomon/decode_rs.c
@@ -42,8 +42,18 @@
 	BUG_ON(pad < 0 || pad >= nn);
 
 	/* Does the caller provide the syndrome ? */
-	if (s != NULL)
-		goto decode;
+	if (s != NULL) {
+		for (i = 0; i < nroots; i++) {
+			/* The syndrome is in index form,
+			 * so nn represents zero
+			 */
+			if (s[i] != nn)
+				goto decode;
+		}
+
+		/* syndrome is zero, no errors to correct  */
+		return 0;
+	}
 
 	/* form the syndromes; i.e., evaluate data(x) at roots of
 	 * g(x) */