Re: [PATCH] mm/vmalloc: Do not trigger BUG() on BH disabled context

[Andrew Morton]

On Fri, 15 May 2026 17:30:09 +0200 "Uladzislau Rezki (Sony)" <urezki@xxxxxxxxx> wrote:

> __get_vm_area_node() currently triggers a BUG() if in_interrupt()
> returns true. However, in_interrupt() also reports true when BH
> are disabled.
> 
> The bridge code can call rhashtable_lookup_insert_fast() with
> bottom halves disabled:
> 
> __vlan_add()
>  -> br_fdb_add_local()
>   spin_lock_bh(&br->hash_lock); <-- Disable BH
>    -> fdb_add_local()
>     -> fdb_create()
>      -> rhashtable_lookup_insert_fast()
>       -> kvmalloc()
>        -> vmalloc()
>         -> __get_vm_area_node()
>          -> BUG_ON(in_interrupt())
>   spin_unlock_bh(&br->hash_lock)
> 
> this triggers the BUG() despite the caller not being in NMI or
> hard IRQ context.
> 
> Replace the in_interrupt() check with in_nmi() || in_hardirq().
> 
> Cc: Ido Schimmel <idosch@xxxxxxxxxx>
> Fixes: c6307674ed82 ("mm: kvmalloc: add non-blocking support for vmalloc")

Was added in 6.19 so I assumed we want cc:stable on this.

> Reported-by: syzbot+8b12fc6e0fb139765b58@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://lore.kernel.org/all/69ff8c7c.050a0220.1036b8.000b.GAE@xxxxxxxxxx/
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>