From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Haoqin Huang <haoqinhuang7@gmail.com>
Cc: minchan@kernel.org, senozhatsky@chromium.org, axboe@kernel.dk,
terrelln@fb.com, dsterba@suse.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
rongwei.wrw@gmail.com, Haoqin Huang <haoqinhuang@tencent.com>,
Rongwei Wang <zigiwang@tencent.com>
Subject: Re: [PATCH 1/3] zram: fix zstd dict use-after-free on per-CPU error path
Date: Fri, 24 Jul 2026 14:17:37 +0900 [thread overview]
Message-ID: <amL0Mb8NN4DhPgKm@google.com> (raw)
In-Reply-To: <20260627070216.13511-1-haoqinhuang7@gmail.com>
On (26/06/27 15:02), Haoqin Huang wrote:
> zstd_setup_params() creates global cdict and ddict stored in
> params->drv_data, shared across all per-CPU contexts. When a
> per-CPU zstd_create() failed, its error path called
> zstd_release_params() which freed those shared objects while
> other per-CPU contexts might already hold references to them.
zstd_release_params() sets ->drv_data to NULL so we can free params
only once. In addition, "while other per-CPU contexts might
already hold references to them" -- other CPUs cannot do anything
with those params, the device is not setup and we cannot handle any
IO requests, right? There is no double-free nor UAF there as far
as I can tell.
> Remove the premature zstd_release_params() from the per-CPU
> error path, the global cdict/ddict are properly released later
> by zstd_release_params(), called from zcomp_init()'s cleanup
> or from zcomp_destroy().
>
> Fixes: 6a559ecd6e7e ("zram: add dictionary support to zstd backend")
What exactly does this fix?
prev parent reply other threads:[~2026-07-24 5:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-27 7:02 [PATCH 1/3] zram: fix zstd dict use-after-free on per-CPU error path Haoqin Huang
2026-06-27 7:02 ` [PATCH 2/3] zram: add per-backend capability flags and validate parameters early Haoqin Huang
2026-07-24 5:27 ` Sergey Senozhatsky
2026-06-27 7:02 ` [PATCH 3/3] zram: reset per-priority params when changing algorithm before init Haoqin Huang
2026-07-24 5:19 ` Sergey Senozhatsky
2026-07-07 7:19 ` [PATCH 1/3] zram: fix zstd dict use-after-free on per-CPU error path Sergey Senozhatsky
2026-07-24 5:17 ` Sergey Senozhatsky [this message]
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