linux-kernel - [PATCH] btrfs: zlib: zero-initialize zlib workspace

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Message-ID: <20230124113234.2070729-1-glider@google.com>
Date:   Tue, 24 Jan 2023 12:32:34 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com
Cc:     clm@...com, dsterba@...e.com, josef@...icpanda.com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        ebiggers@...nel.org,
        syzbot+14d9e7602ebdf7ec0a60@...kaller.appspotmail.com
Subject: [PATCH] btrfs: zlib: zero-initialize zlib workspace

KMSAN reports uses of uninitialized memory in zlib's longest_match()
called on memory originating from zlib_alloc_workspace().
This issue is known by zlib maintainers and is claimed to be harmless,
but to be on the safe side we'd better initialize the memory.

Link: https://zlib.net/zlib_faq.html#faq36
Reported-by: syzbot+14d9e7602ebdf7ec0a60@...kaller.appspotmail.com
Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
 fs/btrfs/zlib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 01a13de118320..da7bb9187b68a 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -63,7 +63,7 @@ struct list_head *zlib_alloc_workspace(unsigned int level)
 
 	workspacesize = max(zlib_deflate_workspacesize(MAX_WBITS, MAX_MEM_LEVEL),
 			zlib_inflate_workspacesize());
-	workspace->strm.workspace = kvmalloc(workspacesize, GFP_KERNEL);
+	workspace->strm.workspace = kvzalloc(workspacesize, GFP_KERNEL);
 	workspace->level = level;
 	workspace->buf = NULL;
 	/*
-- 
2.39.0.246.g2a6d74b583-goog