kernel/linux.git/net/core/skbuff.c, branch linux-5.11.y

net: expand textsearch ts_state to fit skb_seq_state

2021-03-17T16:11:42+00:00

[ Upstream commit b228c9b058760500fda5edb3134527f629fc2dc3 ] The referenced commit expands the skb_seq_state used by skb_find_text with a 4B frag_off field, growing it to 48B. This exceeds container ts_state->cb, causing a stack corruption: [ 73.238353] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: skb_find_text+0xc5/0xd0 [ 73.247384] CPU: 1 PID: 376 Comm: nping Not tainted 5.11.0+ #4 [ 73.252613] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 73.260078] Call Trace: [ 73.264677] dump_stack+0x57/0x6a [ 73.267866] panic+0xf6/0x2b7 [ 73.270578] ? skb_find_text+0xc5/0xd0 [ 73.273964] __stack_chk_fail+0x10/0x10 [ 73.277491] skb_find_text+0xc5/0xd0 [ 73.280727] string_mt+0x1f/0x30 [ 73.283639] ipt_do_table+0x214/0x410 The struct is passed between skb_find_text and its callbacks skb_prepare_seq_read, skb_seq_read and skb_abort_seq read through the textsearch interface using TS_SKB_CB. I assumed that this mapped to skb->cb like other .._SKB_CB wrappers. skb->cb is 48B. But it maps to ts_state->cb, which is only 40B. skb->cb was increased from 40B to 48B after ts_state was introduced, in commit 3e3850e989c5 ("[NETFILTER]: Fix xfrm lookup in ip_route_me_harder/ip6_route_me_harder"). Increase ts_state.cb[] to 48 to fit the struct. Also add a BUILD_BUG_ON to avoid a repeat. The alternative is to directly add a dependency from textsearch onto linux/skbuff.h, but I think the intent is textsearch to have no such dependencies on its callers. Link: https://bugzilla.kernel.org/show_bug.cgi?id=211911 Fixes: 97550f6fa592 ("net: compound page support in skb_seq_read") Reported-by: Kris Karas Signed-off-by: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Sasha Levin

net: fix up truesize of cloned skb in skb_prepare_for_shift()

2021-03-07T11:35:45+00:00

commit 097b9146c0e26aabaa6ff3e5ea536a53f5254a79 upstream. Avoid the assumption that ksize(kmalloc(S)) == ksize(kmalloc(S)): when cloning an skb, save and restore truesize after pskb_expand_head(). This can occur if the allocator decides to service an allocation of the same size differently (e.g. use a different size class, or pass the allocation on to KFENCE). Because truesize is used for bookkeeping (such as sk_wmem_queued), a modified truesize of a cloned skb may result in corrupt bookkeeping and relevant warnings (such as in sk_stream_kill_queues()). Link: https://lkml.kernel.org/r/X9JR/J6dMMOy1obu@elver.google.com Reported-by: syzbot+7b99aafdcc2eedea6178@syzkaller.appspotmail.com Suggested-by: Eric Dumazet Signed-off-by: Marco Elver Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/r/20210201160420.2826895-1-elver@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

skbuff: back tiny skbs with kmalloc() in __netdev_alloc_skb() too

2021-01-17T03:02:04+00:00

Commit 3226b158e67c ("net: avoid 32 x truesize under-estimation for tiny skbs") ensured that skbs with data size lower than 1025 bytes will be kmalloc'ed to avoid excessive page cache fragmentation and memory consumption. However, the fix adressed only __napi_alloc_skb() (primarily for virtio_net and napi_get_frags()), but the issue can still be achieved through __netdev_alloc_skb(), which is still used by several drivers. Drivers often allocate a tiny skb for headers and place the rest of the frame to frags (so-called copybreak). Mirror the condition to __netdev_alloc_skb() to handle this case too. Since v1 [0]: - fix "Fixes:" tag; - refine commit message (mention copybreak usecase). [0] https://lore.kernel.org/netdev/20210114235423.232737-1-alobakin@pm.me Fixes: a1c7fff7e18f ("net: netdev_alloc_skb() use build_skb()") Signed-off-by: Alexander Lobakin Link: https://lore.kernel.org/r/20210115150354.85967-1-alobakin@pm.me Signed-off-by: Jakub Kicinski

net: avoid 32 x truesize under-estimation for tiny skbs

2021-01-14T18:51:52+00:00

Both virtio net and napi_get_frags() allocate skbs with a very small skb->head While using page fragments instead of a kmalloc backed skb->head might give a small performance improvement in some cases, there is a huge risk of under estimating memory usage. For both GOOD_COPY_LEN and GRO_MAX_HEAD, we can fit at least 32 allocations per page (order-3 page in x86), or even 64 on PowerPC We have been tracking OOM issues on GKE hosts hitting tcp_mem limits but consuming far more memory for TCP buffers than instructed in tcp_mem[2] Even if we force napi_alloc_skb() to only use order-0 pages, the issue would still be there on arches with PAGE_SIZE >= 32768 This patch makes sure that small skb head are kmalloc backed, so that other objects in the slab page can be reused instead of being held as long as skbs are sitting in socket queues. Note that we might in the future use the sk_buff napi cache, instead of going through a more expensive __alloc_skb() Another idea would be to use separate page sizes depending on the allocated length (to never have more than 4 frags per page) I would like to thank Greg Thelen for his precious help on this matter, analysing crash dumps is always a time consuming task. Fixes: fd11a83dd363 ("net: Pull out core bits of __netdev_alloc_skb and add __napi_alloc_skb") Signed-off-by: Eric Dumazet Cc: Paolo Abeni Cc: Greg Thelen Reviewed-by: Alexander Duyck Acked-by: Michael S. Tsirkin Link: https://lore.kernel.org/r/20210113161819.1155526-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski

net: compound page support in skb_seq_read

2021-01-12T02:20:09+00:00

skb_seq_read iterates over an skb, returning pointer and length of the next data range with each call. It relies on kmap_atomic to access highmem pages when needed. An skb frag may be backed by a compound page, but kmap_atomic maps only a single page. There are not enough kmap slots to always map all pages concurrently. Instead, if kmap_atomic is needed, iterate over each page. As this increases the number of calls, avoid this unless needed. The necessary condition is captured in skb_frag_must_loop. I tried to make the change as obvious as possible. It should be easy to verify that nothing changes if skb_frag_must_loop returns false. Tested: On an x86 platform with CONFIG_HIGHMEM=y CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP=y CONFIG_NETFILTER_XT_MATCH_STRING=y Run ip link set dev lo mtu 1500 iptables -A OUTPUT -m string --string 'badstring' -algo bm -j ACCEPT dd if=/dev/urandom of=in bs=1M count=20 nc -l -p 8000 > /dev/null & nc -w 1 -q 0 localhost 8000 < in Signed-off-by: Willem de Bruijn Signed-off-by: Jakub Kicinski

net: fix use-after-free when UDP GRO with shared fraglist

2021-01-09T03:14:02+00:00

skbs in fraglist could be shared by a BPF filter loaded at TC. If TC writes, it will call skb_ensure_writable -> pskb_expand_head to create a private linear section for the head_skb. And then call skb_clone_fraglist -> skb_get on each skb in the fraglist. skb_segment_list overwrites part of the skb linear section of each fragment itself. Even after skb_clone, the frag_skbs share their linear section with their clone in PF_PACKET. Both sk_receive_queue of PF_PACKET and PF_INET (or PF_INET6) can have a link for the same frag_skbs chain. If a new skb (not frags) is queued to one of the sk_receive_queue, multiple ptypes can see and release this. It causes use-after-free. [ 4443.426215] ------------[ cut here ]------------ [ 4443.426222] refcount_t: underflow; use-after-free. [ 4443.426291] WARNING: CPU: 7 PID: 28161 at lib/refcount.c:190 refcount_dec_and_test_checked+0xa4/0xc8 [ 4443.426726] pstate: 60400005 (nZCv daif +PAN -UAO) [ 4443.426732] pc : refcount_dec_and_test_checked+0xa4/0xc8 [ 4443.426737] lr : refcount_dec_and_test_checked+0xa0/0xc8 [ 4443.426808] Call trace: [ 4443.426813] refcount_dec_and_test_checked+0xa4/0xc8 [ 4443.426823] skb_release_data+0x144/0x264 [ 4443.426828] kfree_skb+0x58/0xc4 [ 4443.426832] skb_queue_purge+0x64/0x9c [ 4443.426844] packet_set_ring+0x5f0/0x820 [ 4443.426849] packet_setsockopt+0x5a4/0xcd0 [ 4443.426853] __sys_setsockopt+0x188/0x278 [ 4443.426858] __arm64_sys_setsockopt+0x28/0x38 [ 4443.426869] el0_svc_common+0xf0/0x1d0 [ 4443.426873] el0_svc_handler+0x74/0x98 [ 4443.426880] el0_svc+0x8/0xc Fixes: 3a1296a38d0c (net: Support GRO/GSO fraglist chaining.) Signed-off-by: Dongseok Yi Acked-by: Willem de Bruijn Acked-by: Daniel Borkmann Link: https://lore.kernel.org/r/1610072918-174177-1-git-send-email-dseok.yi@samsung.com Signed-off-by: Jakub Kicinski

net: drop bogus skb with CHECKSUM_PARTIAL and offset beyond end of trimmed packet

2020-12-15T02:41:01+00:00

syzbot reproduces BUG_ON in skb_checksum_help(): tun creates (bogus) skb with huge partial-checksummed area and small ip packet inside. Then ip_rcv trims the skb based on size of internal ip packet, after that csum offset points beyond of trimmed skb. Then checksum_tg() called via netfilter hook triggers BUG_ON: offset = skb_checksum_start_offset(skb); BUG_ON(offset >= skb_headlen(skb)); To work around the problem this patch forces pskb_trim_rcsum_slow() to return -EINVAL in described scenario. It allows its callers to drop such kind of packets. Link: https://syzkaller.appspot.com/bug?id=b419a5ca95062664fe1a60b764621eb4526e2cd0 Reported-by: syzbot+7010af67ced6105e5ab6@syzkaller.appspotmail.com Signed-off-by: Vasily Averin Acked-by: Willem de Bruijn Link: https://lore.kernel.org/r/1b2494af-2c56-8ee2-7bc0-923fcad1cdf8@virtuozzo.com Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2020-12-03T23:44:09+00:00

Conflicts: drivers/net/ethernet/ibm/ibmvnic.c Signed-off-by: Jakub Kicinski

net: skbuff: ensure LSE is pullable before decrementing the MPLS ttl

2020-12-03T19:13:21+00:00

skb_mpls_dec_ttl() reads the LSE without ensuring that it is contained in the skb "linear" area. Fix this calling pskb_may_pull() before reading the current ttl. Found by code inspection. Fixes: 2a2ea50870ba ("net: sched: add mpls manipulation actions to TC") Reported-by: Marcelo Ricardo Leitner Signed-off-by: Davide Caratti Link: https://lore.kernel.org/r/53659f28be8bc336c113b5254dc637cc76bbae91.1606987074.git.dcaratti@redhat.com Signed-off-by: Jakub Kicinski

net: switch to storing KCOV handle directly in sk_buff

2020-12-01T19:26:19+00:00

It turns out that usage of skb extensions can cause memory leaks. Ido Schimmel reported: "[...] there are instances that blindly overwrite 'skb->extensions' by invoking skb_copy_header() after __alloc_skb()." Therefore, give up on using skb extensions for KCOV handle, and instead directly store kcov_handle in sk_buff. Fixes: 6370cc3bbd8a ("net: add kcov handle to skb extensions") Fixes: 85ce50d337d1 ("net: kcov: don't select SKB_EXTENSIONS when there is no NET") Fixes: 97f53a08cba1 ("net: linux/skbuff.h: combine SKB_EXTENSIONS + KCOV handling") Link: https://lore.kernel.org/linux-wireless/20201121160941.GA485907@shredder.lan/ Reported-by: Ido Schimmel Signed-off-by: Marco Elver Link: https://lore.kernel.org/r/20201125224840.2014773-1-elver@google.com Signed-off-by: Jakub Kicinski