linux/include/net/icmp.h

64 lines
1.9 KiB

ipv4: icmp: Pass IPv4 control block structure as an argument to __icmp_send() __icmp_send() is used to generate ICMP error messages in response to various situations such as MTU errors (i.e., "Fragmentation Required") and too many hops (i.e., "Time Exceeded"). The skb that generated the error does not necessarily come from the IPv4 layer and does not always have a valid IPv4 control block in skb->cb. Therefore, commit 9ef6b42ad6fd ("net: Add __icmp_send helper.") changed the function to take the IP options structure as argument instead of deriving it from the skb's control block. Some callers of this function such as icmp_send() pass the IP options structure from the skb's control block as in these call paths the control block is known to be valid, but other callers simply pass a zeroed structure. A subsequent patch will need __icmp_send() to access more information from the IPv4 control block (specifically, the ifindex of the input interface). As a preparation for this change, change the function to take the IPv4 control block structure as an argument instead of the IP options structure. This makes the function similar to its IPv6 counterpart that already takes the IPv6 control block structure as an argument. No functional changes intended. Reviewed-by: Petr Machata <petrm@nvidia.com> Reviewed-by: David Ahern <dsahern@kernel.org> Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20250908073238.119240-3-idosch@nvidia.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-09-08 10:32:32 +03:00
ipv4: icmp: Pass IPv4 control block structure as an argument to __icmp_send() __icmp_send() is used to generate ICMP error messages in response to various situations such as MTU errors (i.e., "Fragmentation Required") and too many hops (i.e., "Time Exceeded"). The skb that generated the error does not necessarily come from the IPv4 layer and does not always have a valid IPv4 control block in skb->cb. Therefore, commit 9ef6b42ad6fd ("net: Add __icmp_send helper.") changed the function to take the IP options structure as argument instead of deriving it from the skb's control block. Some callers of this function such as icmp_send() pass the IP options structure from the skb's control block as in these call paths the control block is known to be valid, but other callers simply pass a zeroed structure. A subsequent patch will need __icmp_send() to access more information from the IPv4 control block (specifically, the ifindex of the input interface). As a preparation for this change, change the function to take the IPv4 control block structure as an argument instead of the IP options structure. This makes the function similar to its IPv6 counterpart that already takes the IPv6 control block structure as an argument. No functional changes intended. Reviewed-by: Petr Machata <petrm@nvidia.com> Reviewed-by: David Ahern <dsahern@kernel.org> Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20250908073238.119240-3-idosch@nvidia.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-09-08 10:32:32 +03:00
net: icmp: pass zeroed opts from icmp{,v6}_ndo_send before sending The icmp{,v6}_send functions make all sorts of use of skb->cb, casting it with IPCB or IP6CB, assuming the skb to have come directly from the inet layer. But when the packet comes from the ndo layer, especially when forwarded, there's no telling what might be in skb->cb at that point. As a result, the icmp sending code risks reading bogus memory contents, which can result in nasty stack overflows such as this one reported by a user: panic+0x108/0x2ea __stack_chk_fail+0x14/0x20 __icmp_send+0x5bd/0x5c0 icmp_ndo_send+0x148/0x160 In icmp_send, skb->cb is cast with IPCB and an ip_options struct is read from it. The optlen parameter there is of particular note, as it can induce writes beyond bounds. There are quite a few ways that can happen in __ip_options_echo. For example: // sptr/skb are attacker-controlled skb bytes sptr = skb_network_header(skb); // dptr/dopt points to stack memory allocated by __icmp_send dptr = dopt->__data; // sopt is the corrupt skb->cb in question if (sopt->rr) { optlen = sptr[sopt->rr+1]; // corrupt skb->cb + skb->data soffset = sptr[sopt->rr+2]; // corrupt skb->cb + skb->data // this now writes potentially attacker-controlled data, over // flowing the stack: memcpy(dptr, sptr+sopt->rr, optlen); } In the icmpv6_send case, the story is similar, but not as dire, as only IP6CB(skb)->iif and IP6CB(skb)->dsthao are used. The dsthao case is worse than the iif case, but it is passed to ipv6_find_tlv, which does a bit of bounds checking on the value. This is easy to simulate by doing a `memset(skb->cb, 0x41, sizeof(skb->cb));` before calling icmp{,v6}_ndo_send, and it's only by good fortune and the rarity of icmp sending from that context that we've avoided reports like this until now. For example, in KASAN: BUG: KASAN: stack-out-of-bounds in __ip_options_echo+0xa0e/0x12b0 Write of size 38 at addr ffff888006f1f80e by task ping/89 CPU: 2 PID: 89 Comm: ping Not tainted 5.10.0-rc7-debug+ #5 Call Trace: dump_stack+0x9a/0xcc print_address_description.constprop.0+0x1a/0x160 __kasan_report.cold+0x20/0x38 kasan_report+0x32/0x40 check_memory_region+0x145/0x1a0 memcpy+0x39/0x60 __ip_options_echo+0xa0e/0x12b0 __icmp_send+0x744/0x1700 Actually, out of the 4 drivers that do this, only gtp zeroed the cb for the v4 case, while the rest did not. So this commit actually removes the gtp-specific zeroing, while putting the code where it belongs in the shared infrastructure of icmp{,v6}_ndo_send. This commit fixes the issue by passing an empty IPCB or IP6CB along to the functions that actually do the work. For the icmp_send, this was already trivial, thanks to __icmp_send providing the plumbing function. For icmpv6_send, this required a tiny bit of refactoring to make it behave like the v4 case, after which it was straight forward. Fixes: a2b78e9b2cac ("sunvnet: generate ICMP PTMUD messages for smaller port MTUs") Reported-by: SinYu <liuxyon@gmail.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Link: https://lore.kernel.org/netdev/CAF=yD-LOF116aHub6RMe8vB8ZpnrrnoTdqhobEx+bvoA8AsP0w@mail.gmail.com/T/ Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Link: https://lore.kernel.org/r/20210223131858.72082-1-Jason@zx2c4.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-02-23 14:18:58 +01:00
ipv4: icmp: Pass IPv4 control block structure as an argument to __icmp_send() __icmp_send() is used to generate ICMP error messages in response to various situations such as MTU errors (i.e., "Fragmentation Required") and too many hops (i.e., "Time Exceeded"). The skb that generated the error does not necessarily come from the IPv4 layer and does not always have a valid IPv4 control block in skb->cb. Therefore, commit 9ef6b42ad6fd ("net: Add __icmp_send helper.") changed the function to take the IP options structure as argument instead of deriving it from the skb's control block. Some callers of this function such as icmp_send() pass the IP options structure from the skb's control block as in these call paths the control block is known to be valid, but other callers simply pass a zeroed structure. A subsequent patch will need __icmp_send() to access more information from the IPv4 control block (specifically, the ifindex of the input interface). As a preparation for this change, change the function to take the IPv4 control block structure as an argument instead of the IP options structure. This makes the function similar to its IPv6 counterpart that already takes the IPv6 control block structure as an argument. No functional changes intended. Reviewed-by: Petr Machata <petrm@nvidia.com> Reviewed-by: David Ahern <dsahern@kernel.org> Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20250908073238.119240-3-idosch@nvidia.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-09-08 10:32:32 +03:00
net: icmp: pass zeroed opts from icmp{,v6}_ndo_send before sending The icmp{,v6}_send functions make all sorts of use of skb->cb, casting it with IPCB or IP6CB, assuming the skb to have come directly from the inet layer. But when the packet comes from the ndo layer, especially when forwarded, there's no telling what might be in skb->cb at that point. As a result, the icmp sending code risks reading bogus memory contents, which can result in nasty stack overflows such as this one reported by a user: panic+0x108/0x2ea __stack_chk_fail+0x14/0x20 __icmp_send+0x5bd/0x5c0 icmp_ndo_send+0x148/0x160 In icmp_send, skb->cb is cast with IPCB and an ip_options struct is read from it. The optlen parameter there is of particular note, as it can induce writes beyond bounds. There are quite a few ways that can happen in __ip_options_echo. For example: // sptr/skb are attacker-controlled skb bytes sptr = skb_network_header(skb); // dptr/dopt points to stack memory allocated by __icmp_send dptr = dopt->__data; // sopt is the corrupt skb->cb in question if (sopt->rr) { optlen = sptr[sopt->rr+1]; // corrupt skb->cb + skb->data soffset = sptr[sopt->rr+2]; // corrupt skb->cb + skb->data // this now writes potentially attacker-controlled data, over // flowing the stack: memcpy(dptr, sptr+sopt->rr, optlen); } In the icmpv6_send case, the story is similar, but not as dire, as only IP6CB(skb)->iif and IP6CB(skb)->dsthao are used. The dsthao case is worse than the iif case, but it is passed to ipv6_find_tlv, which does a bit of bounds checking on the value. This is easy to simulate by doing a `memset(skb->cb, 0x41, sizeof(skb->cb));` before calling icmp{,v6}_ndo_send, and it's only by good fortune and the rarity of icmp sending from that context that we've avoided reports like this until now. For example, in KASAN: BUG: KASAN: stack-out-of-bounds in __ip_options_echo+0xa0e/0x12b0 Write of size 38 at addr ffff888006f1f80e by task ping/89 CPU: 2 PID: 89 Comm: ping Not tainted 5.10.0-rc7-debug+ #5 Call Trace: dump_stack+0x9a/0xcc print_address_description.constprop.0+0x1a/0x160 __kasan_report.cold+0x20/0x38 kasan_report+0x32/0x40 check_memory_region+0x145/0x1a0 memcpy+0x39/0x60 __ip_options_echo+0xa0e/0x12b0 __icmp_send+0x744/0x1700 Actually, out of the 4 drivers that do this, only gtp zeroed the cb for the v4 case, while the rest did not. So this commit actually removes the gtp-specific zeroing, while putting the code where it belongs in the shared infrastructure of icmp{,v6}_ndo_send. This commit fixes the issue by passing an empty IPCB or IP6CB along to the functions that actually do the work. For the icmp_send, this was already trivial, thanks to __icmp_send providing the plumbing function. For icmpv6_send, this required a tiny bit of refactoring to make it behave like the v4 case, after which it was straight forward. Fixes: a2b78e9b2cac ("sunvnet: generate ICMP PTMUD messages for smaller port MTUs") Reported-by: SinYu <liuxyon@gmail.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Link: https://lore.kernel.org/netdev/CAF=yD-LOF116aHub6RMe8vB8ZpnrrnoTdqhobEx+bvoA8AsP0w@mail.gmail.com/T/ Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Link: https://lore.kernel.org/r/20210223131858.72082-1-Jason@zx2c4.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-02-23 14:18:58 +01:00