linux-kernel - [PATCH] pNFS: fix uninitialized pointer access

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Message-ID: <20250716143848.14713-1-antonio@mandelbit.com>
Date: Wed, 16 Jul 2025 16:38:48 +0200
From: Antonio Quartulli <antonio@...delbit.com>
To: linux-nfs@...r.kernel.org
Cc: Antonio Quartulli <antonio@...delbit.com>,
	Trond Myklebust <trondmy@...nel.org>,
	Anna Schumaker <anna@...nel.org>,
	Sergey Bashirov <sergeybashirov@...il.com>,
	Konstantin Evtushenko <koevtushenko@...dex.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] pNFS: fix uninitialized pointer access

In ext_tree_encode_commit() if no block extent is encoded due to lack
of buffer space, ret is set to -ENOSPC and we end up accessing be_prev
despite it being uninitialized.

Fix this behaviour by bailing out right away when no extent is encoded.

Fixes: d84c4754f874 ("pNFS: Fix extent encoding in block/scsi layout")
Addresses-Coverity-ID: 1647611 ("Memory - illegal accesses  (UNINIT)")
Signed-off-by: Antonio Quartulli <antonio@...delbit.com>
---
 fs/nfs/blocklayout/extent_tree.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/nfs/blocklayout/extent_tree.c b/fs/nfs/blocklayout/extent_tree.c
index 315949a7e92d..82e19205f425 100644
--- a/fs/nfs/blocklayout/extent_tree.c
+++ b/fs/nfs/blocklayout/extent_tree.c
@@ -598,6 +598,11 @@ ext_tree_encode_commit(struct pnfs_block_layout *bl, __be32 *p,
 		if (ext_tree_layoutupdate_size(bl, *count) > buffer_size) {
 			(*count)--;
 			ret = -ENOSPC;
+			/* bail out right away if no extent was encoded */
+			if (!*count) {
+				spin_unlock(&bl->bl_ext_lock);
+				return ret;
+			}
 			break;
 		}
 
-- 
2.49.1