From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.3 required=3.0 tests=BAYES_00, BUG6152_INVALID_DATE_TZ_ABSURD,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,INVALID_DATE_TZ_ABSURD, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71496C4727D for ; Sat, 26 Sep 2020 01:55:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2EDD92076D for ; Sat, 26 Sep 2020 01:55:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="nXTlhh98"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="9DowO4+k" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729909AbgIZBz3 (ORCPT ); Fri, 25 Sep 2020 21:55:29 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:59934 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728935AbgIZBz3 (ORCPT ); Fri, 25 Sep 2020 21:55:29 -0400 From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1601085327; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PMH1iCSI0bSlnkbseT2XAxzCdW+t7gDKousNENbwy4Y=; b=nXTlhh98a24xdma/cVImTBTQNQA1GLEoMkSUXCx57/JM1m3p0m7l8vPswV8kcB6LjhDGCi TkTVvQjsciNVhkD/lKdmmX6OiEO0fs3QwROwqa5agZKNOnQ4/4v1VSw3wH+0iRmlsH+p4n dbaPqKS7K+P6iZw+kwlgtoOVMpwvbu2SkXe0Gww12afXnhgbZ8533bX5YxNlJ3U5LZSjVA 1nRjv6hsTMYKS95Wq8frdYNDTrlvuq/SZLB9yC5Xld8F1/poXZYUAzfB7NtQ+0dGidoJ98 M8jHZHl9E0D/RUXxtRPWf3GylOoVZKhZdvd2doUYElpglBrmE3no+pSukmWdag== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1601085327; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PMH1iCSI0bSlnkbseT2XAxzCdW+t7gDKousNENbwy4Y=; b=9DowO4+kxIUtnVW6gDRIXsPce8Hxc7A08nEb9sCA0gGuDNAK2gA1Wm7IbmfYTo4YBdNUGe L7G/ZA7ybVfbjWCQ== To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , Marek Szyprowski , linux-kernel@vger.kernel.org Subject: [PATCH next 1/2] printk: avoid and/or handle record truncation Date: Sat, 26 Sep 2020 04:01:25 +0206 Message-Id: <20200926015526.8921-2-john.ogness@linutronix.de> In-Reply-To: <20200926015526.8921-1-john.ogness@linutronix.de> References: <20200926015526.8921-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a reader provides a buffer that is smaller than the message text, the @text_len field of @info will have a value larger than the buffer size. If readers blindly read @text_len bytes of data without checking the size, they will read beyond their buffer. Add this check to record_print_text() to properly recognize when such truncation needs to occur. Add a maximum size argument to the ringbuffer function to extend records so that records can not be created that are larger than the buffer size of readers. When extending records (LOG_CONT), do not extend records beyond LOG_LINE_MAX since that is the maximum size available in the buffers used by consoles and syslog. Fixes: f5f022e53b87 ("printk: reimplement log_cont using record extension") Signed-off-by: John Ogness Reported-by: Marek Szyprowski --- kernel/printk/printk.c | 7 ++++++- kernel/printk/printk_ringbuffer.c | 12 ++++++++++-- kernel/printk/printk_ringbuffer.h | 2 +- 3 files changed, 17 insertions(+), 4 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 78f68b4830dc..270f19b60e6f 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1357,6 +1357,11 @@ static size_t record_print_text(struct printk_record *r, bool syslog, size_t len = 0; char *next; + if (text_len > buf_size) { + text_len = buf_size; + truncated = true; + } + prefix_len = info_print_prefix(r->info, syslog, time, prefix); /* @@ -1911,7 +1916,7 @@ static size_t log_output(int facility, int level, enum log_flags lflags, struct printk_record r; prb_rec_init_wr(&r, text_len); - if (prb_reserve_in_last(&e, prb, &r, caller_id)) { + if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) { memcpy(&r.text_buf[r.info->text_len], text, text_len); r.info->text_len += text_len; if (lflags & LOG_NEWLINE) { diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 13b94b92342e..2493348a1631 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -202,7 +202,8 @@ * // specify additional 5 bytes text space to extend * prb_rec_init_wr(&r, 5); * - * if (prb_reserve_in_last(&e, &test_rb, &r, printk_caller_id())) { + * // try to extend, but only if it does not exceed 32 bytes + * if (prb_reserve_in_last(&e, &test_rb, &r, printk_caller_id()), 32) { * snprintf(&r.text_buf[r.info->text_len], * r.text_buf_size - r.info->text_len, "hello"); * @@ -1309,6 +1310,7 @@ static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring, * @rb: The ringbuffer to re-reserve and extend data in. * @r: The record structure to allocate buffers for. * @caller_id: The caller ID of the caller (reserving writer). + * @max_size: Fail if the extended size would be greater than this. * * This is the public function available to writers to re-reserve and extend * data. @@ -1343,7 +1345,7 @@ static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring, * @r->info->text_len after concatenating. */ bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, - struct printk_record *r, u32 caller_id) + struct printk_record *r, u32 caller_id, unsigned int max_size) { struct prb_desc_ring *desc_ring = &rb->desc_ring; struct printk_info *info; @@ -1389,6 +1391,9 @@ bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer if (!data_check_size(&rb->text_data_ring, r->text_buf_size)) goto fail; + if (r->text_buf_size > max_size) + goto fail; + r->text_buf = data_alloc(rb, &rb->text_data_ring, r->text_buf_size, &d->text_blk_lpos, id); } else { @@ -1410,6 +1415,9 @@ bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer if (!data_check_size(&rb->text_data_ring, r->text_buf_size)) goto fail; + if (r->text_buf_size > max_size) + goto fail; + r->text_buf = data_realloc(rb, &rb->text_data_ring, r->text_buf_size, &d->text_blk_lpos, id); } diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h index 0adaa685d1ca..5dc9d022db07 100644 --- a/kernel/printk/printk_ringbuffer.h +++ b/kernel/printk/printk_ringbuffer.h @@ -303,7 +303,7 @@ static inline void prb_rec_init_wr(struct printk_record *r, bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, struct printk_record *r); bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, - struct printk_record *r, u32 caller_id); + struct printk_record *r, u32 caller_id, unsigned int max_size); void prb_commit(struct prb_reserved_entry *e); void prb_final_commit(struct prb_reserved_entry *e); -- 2.20.1