| Message ID | 20230803190316.2380231-1-andrew.kanner@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | d14eea09edf427fa36bd446f4a3271f99164202f |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next,v5,1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit | expand |
diff --git a/net/core/filter.c b/net/core/filter.c index 06ba0e56e369..28a59596987a 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4116,12 +4116,6 @@ BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset) if (unlikely(data_end > data_hard_end)) return -EINVAL; - /* ALL drivers MUST init xdp->frame_sz, chicken check below */ - if (unlikely(xdp->frame_sz > PAGE_SIZE)) { - WARN_ONCE(1, "Too BIG xdp->frame_sz = %d\n", xdp->frame_sz); - return -EINVAL; - } - if (unlikely(data_end < xdp->data + ETH_HLEN)) return -EINVAL;
Syzkaller reported the following issue: ======================================= Too BIG xdp->frame_sz = 131072 WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121 ____bpf_xdp_adjust_tail net/core/filter.c:4121 [inline] WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121 bpf_xdp_adjust_tail+0x466/0xa10 net/core/filter.c:4103 ... Call Trace: <TASK> bpf_prog_4add87e5301a4105+0x1a/0x1c __bpf_prog_run include/linux/filter.h:600 [inline] bpf_prog_run_xdp include/linux/filter.h:775 [inline] bpf_prog_run_generic_xdp+0x57e/0x11e0 net/core/dev.c:4721 netif_receive_generic_xdp net/core/dev.c:4807 [inline] do_xdp_generic+0x35c/0x770 net/core/dev.c:4866 tun_get_user+0x2340/0x3ca0 drivers/net/tun.c:1919 tun_chr_write_iter+0xe8/0x210 drivers/net/tun.c:2043 call_write_iter include/linux/fs.h:1871 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x650/0xe40 fs/read_write.c:584 ksys_write+0x12f/0x250 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd xdp->frame_sz > PAGE_SIZE check was introduced in commit c8741e2bfe87 ("xdp: Allow bpf_xdp_adjust_tail() to grow packet size"). But Jesper Dangaard Brouer <jbrouer@redhat.com> noted that after introducing the xdp_init_buff() which all XDP driver use - it's safe to remove this check. The original intend was to catch cases where XDP drivers have not been updated to use xdp.frame_sz, but that is not longer a concern (since xdp_init_buff). Running the initial syzkaller repro it was discovered that the contiguous physical memory allocation is used for both xdp paths in tun_get_user(), e.g. tun_build_skb() and tun_alloc_skb(). It was also stated by Jesper Dangaard Brouer <jbrouer@redhat.com> that XDP can work on higher order pages, as long as this is contiguous physical memory (e.g. a page). Reported-and-tested-by: syzbot+f817490f5bd20541b90a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000774b9205f1d8a80d@google.com/T/ Link: https://syzkaller.appspot.com/bug?extid=f817490f5bd20541b90a Link: https://lore.kernel.org/all/20230725155403.796-1-andrew.kanner@gmail.com/T/ Fixes: 43b5169d8355 ("net, xdp: Introduce xdp_init_buff utility routine") Signed-off-by: Andrew Kanner <andrew.kanner@gmail.com> Acked-by: Jesper Dangaard Brouer <hawk@kernel.org> Acked-by: Jason Wang <jasowang@redhat.com> --- Notes (akanner): v5: - same as v4, but cc-ed bpf@vger.kernel.org according to v3->v4 change v4: https://lore.kernel.org/all/20230801220710.464-1-andrew.kanner@gmail.com/T/ - remove bpf_xdp_adjust_tail() check for frame_sz instead. v3: https://lore.kernel.org/all/20230725155403.796-1-andrew.kanner@gmail.com/T/ v2: https://lore.kernel.org/all/20230725153941.653-1-andrew.kanner@gmail.com/T/ v1: https://lore.kernel.org/all/20230724221326.384-1-andrew.kanner@gmail.com/T/ - initial attempts to fix drivers/net/tun.c:tun_get_user(), e.g. tun_build_skb() or tun_alloc_skb(), to not exceed xdp->frame_sz check from net/core/filter.c net/core/filter.c | 6 ------ 1 file changed, 6 deletions(-)