From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x225pYbAmMWO2UGPD3OdU4noonLnWbjakKSYkh+M/JuelFaPu6KqVgRc0dx1EDD5xiy3gfZpt ARC-Seal: i=1; a=rsa-sha256; t=1516611123; cv=none; d=google.com; s=arc-20160816; b=wjTdd4P+OR/r+OKmLZCTGzoBUGMB7Da09YRqI7Ei0Wine8S+EZfYQzZSMR/xvzMyEH IuwmgswCLB/Tck4HORr3Vg+1hvx5mK33jNRQmEh0jXGR3KiDz5lsZBKpWhiKuk/wpjP7 Hu2MxSHSMcG8Y56QfD3MWh9lpzY8QESYoJ/1BVk8kaGqXCoy84vsWdHHapgToAvsIjXb 38Ql+tglShD5ADDVaN8Ev3pmyCROLodhMdax4oYSEFI4iiO6iaHiCH8tMT2qd0AN90cl kQsxyR+k5zPhQ6ymJDtNSNEambFHPz+OceWhCsTg2IvxckO2QRbe92P4uuC9dbG6Vs2k La7g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=rrQ4T9NhjBGgT4nB7EsRJFAZcPbp7ozFuHttmAMI77U=; b=ltA/qr73vc0nQyAyI1WcbejicQg8Sp6bzKF9vcDKOtHdXhVTkEI7e2dGDuGjDGWr91 pnO+jVr6UxF5UOi/3aS/YJu9bdn2is1QyZXdj+XV3cceMzTwSAWfSm3D7lnZm3i8lfVI MEV59Rr7XMFGhPCwyUibNYrGYvKguEhj4n1AzojeQnLUMouAFyDptqHzQ3OW8Br//TSA Zgg2GfD4dvLWjDUaRXG6MRZJgfPSOk681GEcPE93KnqJ1urBiUo9vUgK9iTtkeqs2wTF aqWwYb19yJGiStcTmtTYYHanNYL7Q03xo4glrbMjJmxw2BB6UJ4MEx3S11acIZzW2TAz 0krw== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Joe Lawrence , Mikulas Patocka , Al Viro , Jens Axboe , Michael Kerrisk , Randy Dunlap , Josh Poimboeuf , Andrew Morton , Dong Jinguang , Linus Torvalds Subject: [PATCH 4.14 42/89] pipe: avoid round_pipe_size() nr_pages overflow on 32-bit Date: Mon, 22 Jan 2018 09:45:22 +0100 Message-Id: <20180122083958.888736933@linuxfoundation.org> X-Mailer: git-send-email 2.16.0 In-Reply-To: <20180122083954.683903493@linuxfoundation.org> References: <20180122083954.683903493@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1590281456343064834?= X-GMAIL-MSGID: =?utf-8?q?1590282026046609722?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Joe Lawrence commit d3f14c485867cfb2e0c48aa88c41d0ef4bf5209c upstream. round_pipe_size() contains a right-bit-shift expression which may overflow, which would cause undefined results in a subsequent roundup_pow_of_two() call. static inline unsigned int round_pipe_size(unsigned int size) { unsigned long nr_pages; nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; } PAGE_SIZE is defined as (1UL << PAGE_SHIFT), so: - 4 bytes wide on 32-bit (0 to 0xffffffff) - 8 bytes wide on 64-bit (0 to 0xffffffffffffffff) That means that 32-bit round_pipe_size(), nr_pages may overflow to 0: size=0x00000000 nr_pages=0x0 size=0x00000001 nr_pages=0x1 size=0xfffff000 nr_pages=0xfffff size=0xfffff001 nr_pages=0x0 << ! size=0xffffffff nr_pages=0x0 << ! This is bad because roundup_pow_of_two(n) is undefined when n == 0! 64-bit is not a problem as the unsigned int size is 4 bytes wide (similar to 32-bit) and the larger, 8 byte wide unsigned long, is sufficient to handle the largest value of the bit shift expression: size=0xffffffff nr_pages=100000 Modify round_pipe_size() to return 0 if n == 0 and updates its callers to handle accordingly. Link: http://lkml.kernel.org/r/1507658689-11669-3-git-send-email-joe.lawrence@redhat.com Signed-off-by: Joe Lawrence Reported-by: Mikulas Patocka Reviewed-by: Mikulas Patocka Cc: Al Viro Cc: Jens Axboe Cc: Michael Kerrisk Cc: Randy Dunlap Cc: Josh Poimboeuf Signed-off-by: Andrew Morton Signed-off-by: Dong Jinguang Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/pipe.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) --- a/fs/pipe.c +++ b/fs/pipe.c @@ -1018,13 +1018,19 @@ const struct file_operations pipefifo_fo /* * Currently we rely on the pipe array holding a power-of-2 number - * of pages. + * of pages. Returns 0 on error. */ static inline unsigned int round_pipe_size(unsigned int size) { unsigned long nr_pages; + if (size < pipe_min_size) + size = pipe_min_size; + nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (nr_pages == 0) + return 0; + return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; } @@ -1040,6 +1046,8 @@ static long pipe_set_size(struct pipe_in long ret = 0; size = round_pipe_size(arg); + if (size == 0) + return -EINVAL; nr_pages = size >> PAGE_SHIFT; if (!nr_pages) @@ -1123,13 +1131,18 @@ out_revert_acct: int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, size_t *lenp, loff_t *ppos) { + unsigned int rounded_pipe_max_size; int ret; ret = proc_douintvec_minmax(table, write, buf, lenp, ppos); if (ret < 0 || !write) return ret; - pipe_max_size = round_pipe_size(pipe_max_size); + rounded_pipe_max_size = round_pipe_size(pipe_max_size); + if (rounded_pipe_max_size == 0) + return -EINVAL; + + pipe_max_size = rounded_pipe_max_size; return ret; }