Op do 7 nov 2024 om 15:14 schreef Kalle Valo <kvalo@xxxxxxxxxx>: > > nvbolhuis@xxxxxxxxx writes: > > > From: Norbert van Bolhuis <nvbolhuis@xxxxxxxxx> > > > > 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. > > > > 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. > > > > Signed-off-by: Norbert van Bolhuis <nvbolhuis@xxxxxxxxx> > > What changed from v1? Please include a list of changes after '--' line, > but no need to resend because of this. > Nothing changed, I just added the s-o-b.
