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 186A130F523; Tue, 31 Mar 2026 17:10:01 +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=1774977002; cv=none; b=aZsw6Tjdjkui9I1aD4BUl5nWOfcnWUsxuYDfJGL9hJGR9Ykl2R41XbVSee4CtOuNsFie8b6hwRsQIhjJEEa30AthK76dD/bWkyns5+Sxh8gU90rjA2wBh3IsuCwjNbQrmNaQp82IrUeb5ZGuOWJCntZZWPPHQ0a0nSyxJGOcOsw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774977002; c=relaxed/simple; bh=KMm/VXkD0QUPTJGA9a+jNjEcENb+Vi6HO8hSBF57r8k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p5xXknIqlNR92kfaUqRUIot9JJXs8YEW9ydZ+333kG1IPQZ8WYOPRfFQZTACKhF6plEiqYC1JKEPmK4B/R5KpJHfwDGGALVotRHNHENC9g1lXJ0538nEjtm8/EFdxyBfnQl1s8ddb6N3Lu/i/esXEHGuFLbWrnpNNC4Nyf9Za/A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=auLLQTdA; 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="auLLQTdA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41CB3C19424; Tue, 31 Mar 2026 17:10:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774977001; bh=KMm/VXkD0QUPTJGA9a+jNjEcENb+Vi6HO8hSBF57r8k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=auLLQTdAmPJF+/vgFIrIvp4MNnB7TDZa4sJQRInQMem7bgmSoFeaLRnTaSEJamenF P88urDrw5WgGUsPeVys0kDbMo5pv/Hr4vLSgFn76qopOO7jitxPKytLFJ0ThRY+2K9 QhuK+0et3Bju3Mdl4Esk+9QFlBu+Dtpe8mLiz3jk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, SeongJae Park , Andrew Morton Subject: [PATCH 6.18 278/309] mm/damon/core: avoid use of half-online-committed context Date: Tue, 31 Mar 2026 18:23:01 +0200 Message-ID: <20260331161803.795241676@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161753.468533260@linuxfoundation.org> References: <20260331161753.468533260@linuxfoundation.org> User-Agent: quilt/0.69 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: SeongJae Park commit 26f775a054c3cda86ad465a64141894a90a9e145 upstream. One major usage of damon_call() is online DAMON parameters update. It is done by calling damon_commit_ctx() inside the damon_call() callback function. damon_commit_ctx() can fail for two reasons: 1) invalid parameters and 2) internal memory allocation failures. In case of failures, the damon_ctx that attempted to be updated (commit destination) can be partially updated (or, corrupted from a perspective), and therefore shouldn't be used anymore. The function only ensures the damon_ctx object can safely deallocated using damon_destroy_ctx(). The API callers are, however, calling damon_commit_ctx() only after asserting the parameters are valid, to avoid damon_commit_ctx() fails due to invalid input parameters. But it can still theoretically fail if the internal memory allocation fails. In the case, DAMON may run with the partially updated damon_ctx. This can result in unexpected behaviors including even NULL pointer dereference in case of damos_commit_dests() failure [1]. Such allocation failure is arguably too small to fail, so the real world impact would be rare. But, given the bad consequence, this needs to be fixed. Avoid such partially-committed (maybe-corrupted) damon_ctx use by saving the damon_commit_ctx() failure on the damon_ctx object. For this, introduce damon_ctx->maybe_corrupted field. damon_commit_ctx() sets it when it is failed. kdamond_call() checks if the field is set after each damon_call_control->fn() is executed. If it is set, ignore remaining callback requests and return. All kdamond_call() callers including kdamond_fn() also check the maybe_corrupted field right after kdamond_call() invocations. If the field is set, break the kdamond_fn() main loop so that DAMON sill doesn't use the context that might be corrupted. [sj@kernel.org: let kdamond_call() with cancel regardless of maybe_corrupted] Link: https://lkml.kernel.org/r/20260320031553.2479-1-sj@kernel.org Link: https://sashiko.dev/#/patchset/20260319145218.86197-1-sj%40kernel.org Link: https://lkml.kernel.org/r/20260319145218.86197-1-sj@kernel.org Link: https://lore.kernel.org/20260319043309.97966-1-sj@kernel.org [1] Fixes: 3301f1861d34 ("mm/damon/sysfs: handle commit command using damon_call()") Signed-off-by: SeongJae Park Cc: [6.15+] Signed-off-by: Andrew Morton Signed-off-by: SeongJae Park Signed-off-by: Greg Kroah-Hartman --- include/linux/damon.h | 6 ++++++ mm/damon/core.c | 8 ++++++++ 2 files changed, 14 insertions(+) --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -786,6 +786,12 @@ struct damon_ctx { struct damos_walk_control *walk_control; struct mutex walk_control_lock; + /* + * indicate if this may be corrupted. Currentonly this is set only for + * damon_commit_ctx() failure. + */ + bool maybe_corrupted; + /* public: */ struct task_struct *kdamond; struct mutex kdamond_lock; --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1236,6 +1236,7 @@ int damon_commit_ctx(struct damon_ctx *d { int err; + dst->maybe_corrupted = true; if (!is_power_of_2(src->min_sz_region)) return -EINVAL; @@ -1261,6 +1262,7 @@ int damon_commit_ctx(struct damon_ctx *d dst->addr_unit = src->addr_unit; dst->min_sz_region = src->min_sz_region; + dst->maybe_corrupted = false; return 0; } @@ -2562,6 +2564,8 @@ static void kdamond_call(struct damon_ct } else { list_add(&control->list, &repeat_controls); } + if (!cancel && ctx->maybe_corrupted) + break; } control = list_first_entry_or_null(&repeat_controls, struct damon_call_control, list); @@ -2594,6 +2598,8 @@ static int kdamond_wait_activation(struc kdamond_usleep(min_wait_time); kdamond_call(ctx, false); + if (ctx->maybe_corrupted) + return -EINVAL; damos_walk_cancel(ctx); } return -EBUSY; @@ -2679,6 +2685,8 @@ static int kdamond_fn(void *data) * kdamond_merge_regions() if possible, to reduce overhead */ kdamond_call(ctx, false); + if (ctx->maybe_corrupted) + break; if (!list_empty(&ctx->schemes)) kdamond_apply_schemes(ctx); else