From: Xuan Zhuo xuanzhuo@linux.alibaba.com
[ Upstream commit 5acc7d3e8d342858405fbbc671221f676b547ce7 ]
The problem occurs between dev_get_by_index() and dev_xdp_attach_link(). At this point, dev_xdp_uninstall() is called. Then xdp link will not be detached automatically when dev is released. But link->dev already points to dev, when xdp link is released, dev will still be accessed, but dev has been released.
dev_get_by_index() | link->dev = dev | | rtnl_lock() | unregister_netdevice_many() | dev_xdp_uninstall() | rtnl_unlock() rtnl_lock(); | dev_xdp_attach_link() | rtnl_unlock(); | | netdev_run_todo() // dev released bpf_xdp_link_release() | /* access dev. | use-after-free */ |
[ 45.966867] BUG: KASAN: use-after-free in bpf_xdp_link_release+0x3b8/0x3d0 [ 45.967619] Read of size 8 at addr ffff00000f9980c8 by task a.out/732 [ 45.968297] [ 45.968502] CPU: 1 PID: 732 Comm: a.out Not tainted 5.13.0+ #22 [ 45.969222] Hardware name: linux,dummy-virt (DT) [ 45.969795] Call trace: [ 45.970106] dump_backtrace+0x0/0x4c8 [ 45.970564] show_stack+0x30/0x40 [ 45.970981] dump_stack_lvl+0x120/0x18c [ 45.971470] print_address_description.constprop.0+0x74/0x30c [ 45.972182] kasan_report+0x1e8/0x200 [ 45.972659] __asan_report_load8_noabort+0x2c/0x50 [ 45.973273] bpf_xdp_link_release+0x3b8/0x3d0 [ 45.973834] bpf_link_free+0xd0/0x188 [ 45.974315] bpf_link_put+0x1d0/0x218 [ 45.974790] bpf_link_release+0x3c/0x58 [ 45.975291] __fput+0x20c/0x7e8 [ 45.975706] ____fput+0x24/0x30 [ 45.976117] task_work_run+0x104/0x258 [ 45.976609] do_notify_resume+0x894/0xaf8 [ 45.977121] work_pending+0xc/0x328 [ 45.977575] [ 45.977775] The buggy address belongs to the page: [ 45.978369] page:fffffc00003e6600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4f998 [ 45.979522] flags: 0x7fffe0000000000(node=0|zone=0|lastcpupid=0x3ffff) [ 45.980349] raw: 07fffe0000000000 fffffc00003e6708 ffff0000dac3c010 0000000000000000 [ 45.981309] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 [ 45.982259] page dumped because: kasan: bad access detected [ 45.982948] [ 45.983153] Memory state around the buggy address: [ 45.983753] ffff00000f997f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 45.984645] ffff00000f998000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [ 45.985533] >ffff00000f998080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [ 45.986419] ^ [ 45.987112] ffff00000f998100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [ 45.988006] ffff00000f998180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff [ 45.988895] ================================================================== [ 45.989773] Disabling lock debugging due to kernel taint [ 45.990552] Kernel panic - not syncing: panic_on_warn set ... [ 45.991166] CPU: 1 PID: 732 Comm: a.out Tainted: G B 5.13.0+ #22 [ 45.991929] Hardware name: linux,dummy-virt (DT) [ 45.992448] Call trace: [ 45.992753] dump_backtrace+0x0/0x4c8 [ 45.993208] show_stack+0x30/0x40 [ 45.993627] dump_stack_lvl+0x120/0x18c [ 45.994113] dump_stack+0x1c/0x34 [ 45.994530] panic+0x3a4/0x7d8 [ 45.994930] end_report+0x194/0x198 [ 45.995380] kasan_report+0x134/0x200 [ 45.995850] __asan_report_load8_noabort+0x2c/0x50 [ 45.996453] bpf_xdp_link_release+0x3b8/0x3d0 [ 45.997007] bpf_link_free+0xd0/0x188 [ 45.997474] bpf_link_put+0x1d0/0x218 [ 45.997942] bpf_link_release+0x3c/0x58 [ 45.998429] __fput+0x20c/0x7e8 [ 45.998833] ____fput+0x24/0x30 [ 45.999247] task_work_run+0x104/0x258 [ 45.999731] do_notify_resume+0x894/0xaf8 [ 46.000236] work_pending+0xc/0x328 [ 46.000697] SMP: stopping secondary CPUs [ 46.001226] Dumping ftrace buffer: [ 46.001663] (ftrace buffer empty) [ 46.002110] Kernel Offset: disabled [ 46.002545] CPU features: 0x00000001,23202c00 [ 46.003080] Memory Limit: none
Fixes: aa8d3a716b59db6c ("bpf, xdp: Add bpf_link-based XDP attachment API") Reported-by: Abaci abaci@linux.alibaba.com Signed-off-by: Xuan Zhuo xuanzhuo@linux.alibaba.com Signed-off-by: Alexei Starovoitov ast@kernel.org Reviewed-by: Dust Li dust.li@linux.alibaba.com Acked-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20210710031635.41649-1-xuanzhuo@linux.alibaba.co... Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/dev.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c index 86a0fe0f4c02..4935ca1e887f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -9401,14 +9401,17 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) struct net_device *dev; int err, fd;
+ rtnl_lock(); dev = dev_get_by_index(net, attr->link_create.target_ifindex); - if (!dev) + if (!dev) { + rtnl_unlock(); return -EINVAL; + }
link = kzalloc(sizeof(*link), GFP_USER); if (!link) { err = -ENOMEM; - goto out_put_dev; + goto unlock; }
bpf_link_init(&link->link, BPF_LINK_TYPE_XDP, &bpf_xdp_link_lops, prog); @@ -9418,14 +9421,14 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) err = bpf_link_prime(&link->link, &link_primer); if (err) { kfree(link); - goto out_put_dev; + goto unlock; }
- rtnl_lock(); err = dev_xdp_attach_link(dev, NULL, link); rtnl_unlock();
if (err) { + link->dev = NULL; bpf_link_cleanup(&link_primer); goto out_put_dev; } @@ -9435,6 +9438,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) dev_put(dev); return fd;
+unlock: + rtnl_unlock(); + out_put_dev: dev_put(dev); return err;