CVE-2026-46086
published 2026-05-27CVE-2026-46086: In the Linux kernel, the following vulnerability has been resolved: net: bridge: use a stable FDB dst snapshot in RCU readers Local FDB entries can be…
high7
In the Linux kernel, the following vulnerability has been resolved:
net: bridge: use a stable FDB dst snapshot in RCU readers
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.
Affected
7 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| linux | linux | — | — |
| linux | linux | >= 960b589f86c74ce582922fcb996103271081f4de < 0b9e4bbfb7c949151e3acd44ed4aa33614d2e110 | 0b9e4bbfb7c949151e3acd44ed4aa33614d2e110 |
| linux | linux | >= 960b589f86c74ce582922fcb996103271081f4de < 81af4137a30c4c2dc694dea8cacb180bd66000ef | 81af4137a30c4c2dc694dea8cacb180bd66000ef |
| linux | linux | >= 960b589f86c74ce582922fcb996103271081f4de < 5424e678f9b304e148cf5dcc047cffc7a56a3bb5 | 5424e678f9b304e148cf5dcc047cffc7a56a3bb5 |
| linux | linux | >= 960b589f86c74ce582922fcb996103271081f4de < 9a2d9d4e657b23dc21f24cf139e3aeff0b61341f | 9a2d9d4e657b23dc21f24cf139e3aeff0b61341f |
| linux | linux | >= 960b589f86c74ce582922fcb996103271081f4de < df4601653201de21b487c3e7fffd464790cab808 | df4601653201de21b487c3e7fffd464790cab808 |
| linux | linux_kernel | — | — |