Arend van Spriel <arend.vanspriel@xxxxxxxxxxxx> writes: > On 11/7/2024 9:07 AM, Kalle Valo wrote: > >> Norbert van Bolhuis <nvbolhuis@xxxxxxxxx> writes: >> >>> This patch fixes a NULL pointer dereference bug in brcmfmac that occurs >>> when a high 'sd_sgentry_align' value applies (e.g. 512) and a lot of queued SKBs >>> are sent from the pkt queue. >>> >>> The problem is the number of entries in the pre-allocated sgtable, it is >>> nents = max(rxglom_size, txglom_size) + max(rxglom_size, txglom_size) >> 4 + 1. >>> Given the default [rt]xglom_size=32 it's actually 35 which is too small. >>> Worst case, the pkt queue can end up with 64 SKBs. This occurs when a new SKB >>> is added for each original SKB if tailroom isn't enough to hold tail_pad. >>> At least one sg entry is needed for each SKB. So, eventually the "skb_queue_walk loop" >>> in brcmf_sdiod_sglist_rw may run out of sg entries. This makes sg_next return >>> NULL and this causes the oops. >> BTW it would be good to fix (in a separate patch) the sg handling so >> that the kernel won't oops when sg entries rung. That's not really >> robust behaviour. >> >>> The patch sets nents to max(rxglom_size, txglom_size) * 2 to be able handle >>> the worst-case. >>> Btw. this requires only 64-35=29 * 16 (or 20 if CONFIG_NEED_SG_DMA_LENGTH) = 464 >>> additional bytes of memory. >> s-o-b missing, please read our documentation from the link below. > > I have not seen the actual patch. Which mailing list was it sent to? Only to linux-wireless, adding brcm80211 now. But the patch is in patchwork: https://patchwork.kernel.org/project/linux-wireless/patch/20241105204011.1603148-1-norbert.vanbolhuis@xxxxxxxxxx/ -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
