From patchwork Fri Apr 26 07:34:08 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Tze-nan Wu X-Patchwork-Id: 13644176 Received: from mailgw02.mediatek.com (unknown [210.61.82.184]) (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 367FF13BAFA; Fri, 26 Apr 2024 07:35:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.61.82.184 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714116916; cv=none; b=q0vN9ZDMWnt9TqDhZulYn0igZhWKC1IcUImhmGtVL5M4WbxbQEBq+ncNLDmFZNBKCNAzcjXPNQfIuLnhOkLTz1h8IWxMEo4Z/zoDHmNjs6OGXamJa9nYN9Fe64XYKlWlR0YusaKrOycabutLoilOGGdZQ+C7PEMkBGnf9v6G1cc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714116916; c=relaxed/simple; bh=JXfzjsVtiz3qoFfvvav2iH17WE6d3ogk5w4rd83YZ1Y=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=W680PXLW2PpervRZ3nexUe0mTRA9pi1oXjyGh/69Jlx8kKou4m03rAozF3mvK+uUVlr1pmksn7vC2H6C3YhbhVM0UcUsiZQRb52Dqqr2c9No6Cr8ZX/OH8uFBkVocH5D0Os5LarVbPWQ2I39ew/LYOXOpp3q69md2YHaBNlXUnM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mediatek.com; spf=pass smtp.mailfrom=mediatek.com; dkim=pass (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b=KyPuNyGq; arc=none smtp.client-ip=210.61.82.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mediatek.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mediatek.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=mediatek.com header.i=@mediatek.com header.b="KyPuNyGq" X-UUID: 7f0b9038039f11ef8065b7b53f7091ad-20240426 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:MIME-Version:Message-ID:Date:Subject:CC:To:From; bh=0VnSbfmRmPkE9Z6/xL87FEMZ2565KQXS7kXZBquQw44=; b=KyPuNyGqJD8VkgPAo4mlBIWZoWzeSgaLMTnMYG8mc+B/aY+/P+zZLMCMpccL2wWplka0dGBrkTyenO2a8ZBX9XWo79Z0jJGRlIm+bC9hrzJv2K72dRX9stJ/RscQJ5DnCFQc2VwrmCsRZyanE5HNXLWm4LegkcPSdhhYf2qj73E=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.38,REQID:f34d56c5-3ce9-41bc-b10a-da6caca9e1eb,IP:0,U RL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:0 X-CID-META: VersionHash:82c5f88,CLOUDID:a4612483-4f93-4875-95e7-8c66ea833d57,B ulkID:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0,EDM:-3,IP:nil,U RL:11|1,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES :1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0 X-CID-BVR: 0 X-CID-BAS: 0,_,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR,TF_CID_SPAM_ULN X-UUID: 7f0b9038039f11ef8065b7b53f7091ad-20240426 Received: from mtkmbs14n1.mediatek.inc [(172.21.101.75)] by mailgw02.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1723068776; Fri, 26 Apr 2024 15:35:03 +0800 Received: from mtkmbs13n2.mediatek.inc (172.21.101.108) by mtkmbs10n2.mediatek.inc (172.21.101.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Fri, 26 Apr 2024 15:34:58 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs13n2.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.1118.26 via Frontend Transport; Fri, 26 Apr 2024 15:34:58 +0800 From: Tze-nan wu To: , CC: , , Tze-nan wu , Cheng-Jui Wang , Mathieu Desnoyers , , , , Subject: [PATCH] tracing: Fix uaf issue in tracing_open_file_tr Date: Fri, 26 Apr 2024 15:34:08 +0800 Message-ID: <20240426073410.17154-1-Tze-nan.Wu@mediatek.com> X-Mailer: git-send-email 2.18.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-Product-Ver: SMEX-14.0.0.3152-9.1.1006-23728.005 X-TM-AS-Result: No-10--6.709200-8.000000 X-TMASE-MatchedRID: Oiwj9Z5zoYfBBfeYOfDzGeJmMZmLmwx5JNtuyL6mpIXnQ0faNr22ly2I ryQ4sy22PluEU8uk8U1hIqZMefvkMYHcC7KYYAdEt1AhvyEKdj4Bmf/gD11vZLeKIZi8OZjkOXf Z9OHyzWYYhA/yqU1gbudMv2hWHjOChrD3pNcSx1a4jAucHcCqnTGZtPrBBPZrYTBuC4I3GUdZcq G2bJBnY63QzRpYhGSscAVxZL8H4DMWcPQGe3P9BFVN8laWo90MvtVce6w5+K+7+NPPxj+R6jEdc 33mv6D89ceA9hBhWDteGOFKwHTALzxmES9G+PPgr9glqbqf2bQsleOknNBI0+QydRUvl3QTuBsm 4LkLwbMLVCp/BGC7GAP5V3sWHZfiHG1zuzhqgWfAJnGRMfFxyY/8SyGg0rIRxN4K0DXKS1imRE7 f7OYxUiAgSuPJcYgLWKNxvq78azVveCKWtaLcaNcjCbPZgQnFEVhvB8sXyyPFas8s9VsawZXiR+ iW11ck6kLTNeJvUTbRY2ly55W2vj8J/1ZA8b0wJQI+kfsRJdrq0SQ1Mgx5CCow3ZvJGhxdo8WMk QWv6iXBcIE78YqRWvcUt5lc1lLgoGRyAacnhaaD1+gJoH8joMuF7n2a4giCRdYztKQAnV318qCB RlXuO37cGd19dSFd X-TM-AS-User-Approved-Sender: No X-TM-AS-User-Blocked-Sender: No X-TMASE-Result: 10--6.709200-8.000000 X-TMASE-Version: SMEX-14.0.0.3152-9.1.1006-23728.005 X-TM-SNTS-SMTP: 1855CEFE36B23BD2996F096E4238EF6FD8DFFACC3453EFE8EB7A63622EEEA9672000:8 "tracing_event_file" is at the risk of use-after-free due to the race of two functions "tracing_open_file_tr" and "synth_event_release". Specifically, it could be freed by synth_event_release before tracing_open_file_tr has the opportunity to access its members. It's easy to reproduced by first executing script 'A' and then script 'B' in my environment. Script 'A': echo "hello int aaa" > /sys/kernel/tracing/synthetic_events while : do echo 0 > /sys/kernel/tracing/events/synthetic/hello/enable done Script 'B': echo > /sys/kernel/tracing/synthetic/events My environment: arm64 + generic and swtag based KASAN both enabled + kernel-6.6.18 KASAN report ================================================================== BUG: KASAN: slab-use-after-free in tracing_open_file_tr Read of size 8 at addr 9*ffff********** by task sh/3485 Pointer tag: [9*], memory tag: [fe] CPU: * PID: 3485 Comm: sh Tainted: **************** Call trace: __hwasan_tag_mismatch tracing_open_file_tr do_dentry_open vfs_open path_openat Freed by task 3490: slab_free_freelist_hook kmem_cache_free event_file_put remove_event_file_dir __trace_remove_event_call trace_remove_event_call synth_event_release dyn_events_release_all synth_events_open page last allocated via order 0, migratetype Unmovable: __slab_alloc kmem_cache_alloc trace_create_new_event trace_add_event_call register_synth_event __create_synth_event create_or_delete_synth_event trace_parse_run_command synth_events_write vfs_write Based on the assumption that eventfs_inode will persist throughout the execution of the tracing_open_file_tr function, we can fix this issue by incrementing the reference count of trace_event_file once it is assigned to eventfs_inode->data. The reference count will then be decremented during the release phase of eventfs_inode. This ensures that trace_event_file is not prematurely freed while the tracing_open_file_tr function is being called. Fixes: bb32500fb9b7 ("tracing: Have trace_event_file have ref counters") Co-developed-by: Cheng-Jui Wang Signed-off-by: Cheng-Jui Wang Signed-off-by: Tze-nan wu Tested-by: Tze-nan Wu (吳澤南) --- BTW, I've also attempted to reproduce the same issue in another environment (described below). It's also reproducible but in a lower rate. another environment: x86 + ubuntu + generic kasan enabled + kernel-6.9-rc4 After applying the patch, KASAN no longer reports any issues when following the same reproduction steps in my arm64 environment. However, I am concerned about potential side effects that the patch might introduce. Additionally, the newly added function "is_entry_event_callback" may not be reliable in my opinion, as the callback function used in the comparison could change in future. Nonetheless, this is the best solution I can come up with now. Looking for any suggestion or solution, appreciate. fs/tracefs/event_inode.c | 3 +++ include/linux/trace_events.h | 4 ++++ kernel/trace/trace_events.c | 6 ++++++ 3 files changed, 13 insertions(+) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 894c6ca1e500..fd49c0f88500 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include "internal.h" @@ -90,6 +91,8 @@ static void release_ei(struct kref *ref) kfree(ei->entry_attrs); kfree_const(ei->name); + if (ei->nr_entries && is_entry_event_callback(ei->entries[0])) + event_file_put(ei->data); if (ei->is_events) { rei = get_root_inode(ei); kfree_rcu(rei, ei.rcu); diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 6f9bdfb09d1d..602e87682ee2 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -9,6 +9,7 @@ #include #include #include +#include struct trace_array; struct array_buffer; @@ -505,6 +506,7 @@ extern struct trace_event_file *trace_get_event_file(const char *instance, const char *system, const char *event); extern void trace_put_event_file(struct trace_event_file *file); +bool is_entry_event_callback(struct eventfs_entry entry); #define MAX_DYNEVENT_CMD_LEN (2048) @@ -731,6 +733,8 @@ extern void event_triggers_post_call(struct trace_event_file *file, enum event_trigger_type tt); +extern void event_file_put(struct trace_event_file *file); + bool trace_event_ignore_this_pid(struct trace_event_file *trace_file); bool __trace_trigger_soft_disabled(struct trace_event_file *file); diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 52f75c36bbca..de01676b59ff 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2626,6 +2626,7 @@ event_create_dir(struct eventfs_inode *parent, struct trace_event_file *file) return -1; } + event_file_get(file); file->ei = ei; ret = event_define_fields(call); @@ -3420,6 +3421,11 @@ void trace_put_event_file(struct trace_event_file *file) } EXPORT_SYMBOL_GPL(trace_put_event_file); +bool is_entry_event_callback(struct eventfs_entry entry) +{ + return entry.callback == event_callback; +} + #ifdef CONFIG_DYNAMIC_FTRACE /* Avoid typos */