From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 80E8B268C72; Tue, 8 Apr 2025 12:31:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744115474; cv=none; b=WJvnfj1kPSYQBjYwicE5XlxsU7lhYVltniKNy5QKXwDTWIXzIpXDp36y/lXJvxEEgiGiFh8QlCoFnxKXXaPLKmS8nH710wY2/UsXMbLh1jyaiE9GRJ/MwY/iQSs/cWCsRTsau767m3IXp+ZliW3kb6aBAuZgw5Eu10grneaqwRo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744115474; c=relaxed/simple; bh=oDIRxtXTOAwd03ADdirHXm8X7WTHBS/xzBgKZXbecYw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=M85VqKYmy1AQV861K2WfVDuxC6iHa3GAIQMM0iY+wAVNtJMJyuPUTzVEzioxk+4O0O40pJda4mI3ZUtWfkWyYwObVUTjEZQz56BEIOjOZBjPxrgsktF836gKAJhsVRg3t4YEs9/SvUSbtHL+0I6cdZDlXCiM8+xvTDagksitrww= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tCjG96w/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="tCjG96w/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0EAAC4CEE5; Tue, 8 Apr 2025 12:31:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744115474; bh=oDIRxtXTOAwd03ADdirHXm8X7WTHBS/xzBgKZXbecYw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tCjG96w/jv0fI+7/oyKnWTW/XXxj3LnsAVMheQDYY4AXqkVKovh1FTps4VywacImK CtnOBjP1iqjcEYJbySBcz5xhPSVnVJmO/7VWtTxR/gpL6ULzhouJqt2gJCHuJ7dLAk wjEEdlCn/vDoiJgKKf5Lopqw7UpdK1V/6GJmQH0Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Herbert Xu , Yosry Ahmed , syzbot+1a517ccfcbc6a7ab0f82@syzkaller.appspotmail.com, Chengming Zhou , Nhat Pham , "David S. Miller" , Eric Biggers , Johannes Weiner , Chris Murphy , Andrew Morton Subject: [PATCH 6.13 488/499] mm: zswap: fix crypto_free_acomp() deadlock in zswap_cpu_comp_dead() Date: Tue, 8 Apr 2025 12:51:40 +0200 Message-ID: <20250408104903.529819461@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104851.256868745@linuxfoundation.org> References: <20250408104851.256868745@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yosry Ahmed commit c11bcbc0a517acf69282c8225059b2a8ac5fe628 upstream. Currently, zswap_cpu_comp_dead() calls crypto_free_acomp() while holding the per-CPU acomp_ctx mutex. crypto_free_acomp() then holds scomp_lock (through crypto_exit_scomp_ops_async()). On the other hand, crypto_alloc_acomp_node() holds the scomp_lock (through crypto_scomp_init_tfm()), and then allocates memory. If the allocation results in reclaim, we may attempt to hold the per-CPU acomp_ctx mutex. The above dependencies can cause an ABBA deadlock. For example in the following scenario: (1) Task A running on CPU #1: crypto_alloc_acomp_node() Holds scomp_lock Enters reclaim Reads per_cpu_ptr(pool->acomp_ctx, 1) (2) Task A is descheduled (3) CPU #1 goes offline zswap_cpu_comp_dead(CPU #1) Holds per_cpu_ptr(pool->acomp_ctx, 1)) Calls crypto_free_acomp() Waits for scomp_lock (4) Task A running on CPU #2: Waits for per_cpu_ptr(pool->acomp_ctx, 1) // Read on CPU #1 DEADLOCK Since there is no requirement to call crypto_free_acomp() with the per-CPU acomp_ctx mutex held in zswap_cpu_comp_dead(), move it after the mutex is unlocked. Also move the acomp_request_free() and kfree() calls for consistency and to avoid any potential sublte locking dependencies in the future. With this, only setting acomp_ctx fields to NULL occurs with the mutex held. This is similar to how zswap_cpu_comp_prepare() only initializes acomp_ctx fields with the mutex held, after performing all allocations before holding the mutex. Opportunistically, move the NULL check on acomp_ctx so that it takes place before the mutex dereference. Link: https://lkml.kernel.org/r/20250226185625.2672936-1-yosry.ahmed@linux.dev Fixes: 12dcb0ef5406 ("mm: zswap: properly synchronize freeing resources during CPU hotunplug") Signed-off-by: Herbert Xu Co-developed-by: Herbert Xu Signed-off-by: Yosry Ahmed Reported-by: syzbot+1a517ccfcbc6a7ab0f82@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/67bcea51.050a0220.bbfd1.0096.GAE@google.com/ Acked-by: Herbert Xu Reviewed-by: Chengming Zhou Reviewed-by: Nhat Pham Tested-by: Nhat Pham Cc: David S. Miller Cc: Eric Biggers Cc: Johannes Weiner Cc: Chris Murphy Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/zswap.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) --- a/mm/zswap.c +++ b/mm/zswap.c @@ -881,18 +881,32 @@ static int zswap_cpu_comp_dead(unsigned { struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu); + struct acomp_req *req; + struct crypto_acomp *acomp; + u8 *buffer; + + if (IS_ERR_OR_NULL(acomp_ctx)) + return 0; mutex_lock(&acomp_ctx->mutex); - if (!IS_ERR_OR_NULL(acomp_ctx)) { - if (!IS_ERR_OR_NULL(acomp_ctx->req)) - acomp_request_free(acomp_ctx->req); - acomp_ctx->req = NULL; - if (!IS_ERR_OR_NULL(acomp_ctx->acomp)) - crypto_free_acomp(acomp_ctx->acomp); - kfree(acomp_ctx->buffer); - } + req = acomp_ctx->req; + acomp = acomp_ctx->acomp; + buffer = acomp_ctx->buffer; + acomp_ctx->req = NULL; + acomp_ctx->acomp = NULL; + acomp_ctx->buffer = NULL; mutex_unlock(&acomp_ctx->mutex); + /* + * Do the actual freeing after releasing the mutex to avoid subtle + * locking dependencies causing deadlocks. + */ + if (!IS_ERR_OR_NULL(req)) + acomp_request_free(req); + if (!IS_ERR_OR_NULL(acomp)) + crypto_free_acomp(acomp); + kfree(buffer); + return 0; }