5.4-stable review patch. If anyone has any objections, please let me know.
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From: Charalampos Mitrodimas charmitro@posteo.net
[ Upstream commit 2327a3d6f65ce2fe2634546dde4a25ef52296fec ]
Fix field-spanning memcpy warnings in ah6_output() and ah6_output_done() where extension headers are copied to/from IPv6 address fields, triggering fortify-string warnings about writes beyond the 16-byte address fields.
memcpy: detected field-spanning write (size 40) of single field "&top_iph->saddr" at net/ipv6/ah6.c:439 (size 16) WARNING: CPU: 0 PID: 8838 at net/ipv6/ah6.c:439 ah6_output+0xe7e/0x14e0 net/ipv6/ah6.c:439
The warnings are false positives as the extension headers are intentionally placed after the IPv6 header in memory. Fix by properly copying addresses and extension headers separately, and introduce helper functions to avoid code duplication.
Reported-by: syzbot+01b0667934cdceb4451c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=01b0667934cdceb4451c Signed-off-by: Charalampos Mitrodimas charmitro@posteo.net Signed-off-by: Steffen Klassert steffen.klassert@secunet.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/ah6.c | 50 +++++++++++++++++++++++++++++++------------------- 1 file changed, 31 insertions(+), 19 deletions(-)
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c index 1c5ecd07a43e1..240f46c7ce1e8 100644 --- a/net/ipv6/ah6.c +++ b/net/ipv6/ah6.c @@ -46,6 +46,34 @@ struct ah_skb_cb {
#define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
+/* Helper to save IPv6 addresses and extension headers to temporary storage */ +static inline void ah6_save_hdrs(struct tmp_ext *iph_ext, + struct ipv6hdr *top_iph, int extlen) +{ + if (!extlen) + return; + +#if IS_ENABLED(CONFIG_IPV6_MIP6) + iph_ext->saddr = top_iph->saddr; +#endif + iph_ext->daddr = top_iph->daddr; + memcpy(&iph_ext->hdrs, top_iph + 1, extlen - sizeof(*iph_ext)); +} + +/* Helper to restore IPv6 addresses and extension headers from temporary storage */ +static inline void ah6_restore_hdrs(struct ipv6hdr *top_iph, + struct tmp_ext *iph_ext, int extlen) +{ + if (!extlen) + return; + +#if IS_ENABLED(CONFIG_IPV6_MIP6) + top_iph->saddr = iph_ext->saddr; +#endif + top_iph->daddr = iph_ext->daddr; + memcpy(top_iph + 1, &iph_ext->hdrs, extlen - sizeof(*iph_ext)); +} + static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags, unsigned int size) { @@ -307,13 +335,7 @@ static void ah6_output_done(struct crypto_async_request *base, int err) memcpy(ah->auth_data, icv, ahp->icv_trunc_len); memcpy(top_iph, iph_base, IPV6HDR_BASELEN);
- if (extlen) { -#if IS_ENABLED(CONFIG_IPV6_MIP6) - memcpy(&top_iph->saddr, iph_ext, extlen); -#else - memcpy(&top_iph->daddr, iph_ext, extlen); -#endif - } + ah6_restore_hdrs(top_iph, iph_ext, extlen);
kfree(AH_SKB_CB(skb)->tmp); xfrm_output_resume(skb, err); @@ -384,12 +406,8 @@ static int ah6_output(struct xfrm_state *x, struct sk_buff *skb) */ memcpy(iph_base, top_iph, IPV6HDR_BASELEN);
+ ah6_save_hdrs(iph_ext, top_iph, extlen); if (extlen) { -#if IS_ENABLED(CONFIG_IPV6_MIP6) - memcpy(iph_ext, &top_iph->saddr, extlen); -#else - memcpy(iph_ext, &top_iph->daddr, extlen); -#endif err = ipv6_clear_mutable_options(top_iph, extlen - sizeof(*iph_ext) + sizeof(*top_iph), @@ -440,13 +458,7 @@ static int ah6_output(struct xfrm_state *x, struct sk_buff *skb) memcpy(ah->auth_data, icv, ahp->icv_trunc_len); memcpy(top_iph, iph_base, IPV6HDR_BASELEN);
- if (extlen) { -#if IS_ENABLED(CONFIG_IPV6_MIP6) - memcpy(&top_iph->saddr, iph_ext, extlen); -#else - memcpy(&top_iph->daddr, iph_ext, extlen); -#endif - } + ah6_restore_hdrs(top_iph, iph_ext, extlen);
out_free: kfree(iph_base);