btrfs: zlib: zero-initialize zlib workspace

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

Posted by Alexander Potapenko 2 years, 7 months ago

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@syzkaller.appspotmail.com
Signed-off-by: Alexander Potapenko <glider@google.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

Re: [PATCH] btrfs: zlib: zero-initialize zlib workspace

Posted by David Sterba 2 years, 7 months ago

On Tue, Jan 24, 2023 at 12:32:34PM +0100, Alexander Potapenko wrote:
> 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@syzkaller.appspotmail.com
> Signed-off-by: Alexander Potapenko <glider@google.com>

Added to misc-next, thanks.