mirror of https://github.com/torvalds/linux.git
df46016532
Local FDB entries can be rewritten in place by `fdb_delete_local()`, which
updates `f->dst` to another port or to `NULL` while keeping the entry
alive. Several bridge RCU readers inspect `f->dst`, including
`br_fdb_fillbuf()` through the `brforward_read()` sysfs path.
These readers currently load `f->dst` multiple times and can therefore
observe inconsistent values across the check and later dereference.
In `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change
`f->dst` after the NULL check and before the `port_no` dereference,
leading to a NULL-ptr-deref.
Fix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each
affected RCU reader and using that snapshot for the rest of the access
sequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()`
with `WRITE_ONCE()` so the readers and writer use matching access patterns.
Fixes:
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||
|---|---|---|
| .. | ||
| netfilter | ||
| Kconfig | ||
| Makefile | ||
| br.c | ||
| br_arp_nd_proxy.c | ||
| br_cfm.c | ||
| br_cfm_netlink.c | ||
| br_device.c | ||
| br_fdb.c | ||
| br_forward.c | ||
| br_if.c | ||
| br_input.c | ||
| br_ioctl.c | ||
| br_mdb.c | ||
| br_mrp.c | ||
| br_mrp_netlink.c | ||
| br_mrp_switchdev.c | ||
| br_mst.c | ||
| br_multicast.c | ||
| br_multicast_eht.c | ||
| br_netfilter_hooks.c | ||
| br_netfilter_ipv6.c | ||
| br_netlink.c | ||
| br_netlink_tunnel.c | ||
| br_nf_core.c | ||
| br_private.h | ||
| br_private_cfm.h | ||
| br_private_mcast_eht.h | ||
| br_private_mrp.h | ||
| br_private_stp.h | ||
| br_private_tunnel.h | ||
| br_stp.c | ||
| br_stp_bpdu.c | ||
| br_stp_if.c | ||
| br_stp_timer.c | ||
| br_switchdev.c | ||
| br_sysfs_br.c | ||
| br_sysfs_if.c | ||
| br_vlan.c | ||
| br_vlan_options.c | ||
| br_vlan_tunnel.c | ||