From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx49b38d8yYRnjrv5atZMXfF7+z8Nac52V/D2K4V9yX05qQkbgNWcWlUQuBOZ4P6KpXaseRzv ARC-Seal: i=1; a=rsa-sha256; t=1523473278; cv=none; d=google.com; s=arc-20160816; b=b7PhzBttsk7AVgkiJk+ih2HpQO9FkmEzNX1O/MfJNivHB88reDK2DpX168Q8q7IsYF 1yUTVJM5Al+bRo0mYQuQz/Ld/CVIL6qSuAudjl/RRAMzFCTc7jdoXi2u7Ab2BJp/pUhk c6fdC4l5OE7AMb7rZas3eDE9KO2co4tc8H8l3vxAgklNJQ+IqQDYR425ZjZZl7V7Q98Z 2snq2Xl1z4iR7NfkbYXtkBlfgewWN2iqUd4leWfnk30Y58avlYi6QKZn+h5aBLWZ/mK6 EjlNmP+E1M3/tbxUv8NCHRyFnbICf4KjKrtA8ud3593dtjYYBkrKmEYuLtU2Q+P2eTu7 MugQ== 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=yo1TKBr215CWtfvSdfAw0O+ydtYtNPJlqWWdboDjJs8=; b=G+rxBkhA4MSv0Z6ExjaA1FJo9b0Z04h7xbFapmuhsaegvT1q19epUSKgKeIURz0FsH EmK+a2R6NwVCO6Qwu3LeAs8bJsoSUqozXL2E+AmQTzN7RtoAG7Ntvd/VZ1cxZwI5Q467 9FDleJfh63mXWjwzwLIuM2QHVCA9gtGKEBRhpoMcHXBdI9ZGqL4JsocUb1tT9rX+G9Uf ycmb3d4LO/Kb/0rhYJvoLH2x76gO32pRHciMpeZB5KqWt4z9i/tIrcVdnrv9w2Xf5p+7 oS4anm7KkwJzUcU5hwKvGug6/sDqqvQvoPqE8AbB1RQuslSl+5FvqXxIhb7uUhD5TrNE Q15Q== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 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 90.92.61.202 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, "Jason A. Donenfeld" , Steffen Klassert , Herbert Xu , "David S. Miller" , David Howells , Sabrina Dubroca , "Michael S. Tsirkin" , Jason Wang , Sasha Levin Subject: [PATCH 4.9 190/310] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow Date: Wed, 11 Apr 2018 20:35:29 +0200 Message-Id: <20180411183630.777163220@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180411183622.305902791@linuxfoundation.org> References: <20180411183622.305902791@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review 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?1597476225224312478?= X-GMAIL-MSGID: =?utf-8?q?1597477515970995238?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Jason A. Donenfeld" [ Upstream commit 48a1df65334b74bd7531f932cca5928932abf769 ] This is a defense-in-depth measure in response to bugs like 4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec"). There's not only a potential overflow of sglist items, but also a stack overflow potential, so we fix this by limiting the amount of recursion this function is allowed to do. Not actually providing a bounded base case is a future disaster that we can easily avoid here. As a small matter of house keeping, we take this opportunity to move the documentation comment over the actual function the documentation is for. While this could be implemented by using an explicit stack of skbuffs, when implementing this, the function complexity increased considerably, and I don't think such complexity and bloat is actually worth it. So, instead I built this and tested it on x86, x86_64, ARM, ARM64, and MIPS, and measured the stack usage there. I also reverted the recent MIPS changes that give it a separate IRQ stack, so that I could experience some worst-case situations. I found that limiting it to 24 layers deep yielded a good stack usage with room for safety, as well as being much deeper than any driver actually ever creates. Signed-off-by: Jason A. Donenfeld Cc: Steffen Klassert Cc: Herbert Xu Cc: "David S. Miller" Cc: David Howells Cc: Sabrina Dubroca Cc: "Michael S. Tsirkin" Cc: Jason Wang Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- include/linux/skbuff.h | 8 +++--- net/core/skbuff.c | 65 +++++++++++++++++++++++++++++++------------------ 2 files changed, 46 insertions(+), 27 deletions(-) --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -984,10 +984,10 @@ struct sk_buff *skb_realloc_headroom(str unsigned int headroom); struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom, int newtailroom, gfp_t priority); -int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg, - int offset, int len); -int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, - int len); +int __must_check skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg, + int offset, int len); +int __must_check skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, + int offset, int len); int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer); int skb_pad(struct sk_buff *skb, int pad); #define dev_kfree_skb(a) consume_skb(a) --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3475,24 +3475,18 @@ void __init skb_init(void) NULL); } -/** - * skb_to_sgvec - Fill a scatter-gather list from a socket buffer - * @skb: Socket buffer containing the buffers to be mapped - * @sg: The scatter-gather list to map into - * @offset: The offset into the buffer's contents to start mapping - * @len: Length of buffer space to be mapped - * - * Fill the specified scatter-gather list with mappings/pointers into a - * region of the buffer space attached to a socket buffer. - */ static int -__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) +__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len, + unsigned int recursion_level) { int start = skb_headlen(skb); int i, copy = start - offset; struct sk_buff *frag_iter; int elt = 0; + if (unlikely(recursion_level >= 24)) + return -EMSGSIZE; + if (copy > 0) { if (copy > len) copy = len; @@ -3511,6 +3505,8 @@ __skb_to_sgvec(struct sk_buff *skb, stru end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]); if ((copy = end - offset) > 0) { skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; + if (unlikely(elt && sg_is_last(&sg[elt - 1]))) + return -EMSGSIZE; if (copy > len) copy = len; @@ -3525,16 +3521,22 @@ __skb_to_sgvec(struct sk_buff *skb, stru } skb_walk_frags(skb, frag_iter) { - int end; + int end, ret; WARN_ON(start > offset + len); end = start + frag_iter->len; if ((copy = end - offset) > 0) { + if (unlikely(elt && sg_is_last(&sg[elt - 1]))) + return -EMSGSIZE; + if (copy > len) copy = len; - elt += __skb_to_sgvec(frag_iter, sg+elt, offset - start, - copy); + ret = __skb_to_sgvec(frag_iter, sg+elt, offset - start, + copy, recursion_level + 1); + if (unlikely(ret < 0)) + return ret; + elt += ret; if ((len -= copy) == 0) return elt; offset += copy; @@ -3545,6 +3547,31 @@ __skb_to_sgvec(struct sk_buff *skb, stru return elt; } +/** + * skb_to_sgvec - Fill a scatter-gather list from a socket buffer + * @skb: Socket buffer containing the buffers to be mapped + * @sg: The scatter-gather list to map into + * @offset: The offset into the buffer's contents to start mapping + * @len: Length of buffer space to be mapped + * + * Fill the specified scatter-gather list with mappings/pointers into a + * region of the buffer space attached to a socket buffer. Returns either + * the number of scatterlist items used, or -EMSGSIZE if the contents + * could not fit. + */ +int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) +{ + int nsg = __skb_to_sgvec(skb, sg, offset, len, 0); + + if (nsg <= 0) + return nsg; + + sg_mark_end(&sg[nsg - 1]); + + return nsg; +} +EXPORT_SYMBOL_GPL(skb_to_sgvec); + /* As compared with skb_to_sgvec, skb_to_sgvec_nomark only map skb to given * sglist without mark the sg which contain last skb data as the end. * So the caller can mannipulate sg list as will when padding new data after @@ -3567,19 +3594,11 @@ __skb_to_sgvec(struct sk_buff *skb, stru int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) { - return __skb_to_sgvec(skb, sg, offset, len); + return __skb_to_sgvec(skb, sg, offset, len, 0); } EXPORT_SYMBOL_GPL(skb_to_sgvec_nomark); -int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) -{ - int nsg = __skb_to_sgvec(skb, sg, offset, len); - sg_mark_end(&sg[nsg - 1]); - - return nsg; -} -EXPORT_SYMBOL_GPL(skb_to_sgvec); /** * skb_cow_data - Check that a socket buffer's data buffers are writable