diff mbox series

wifi: brcmfmac: Fix oops due to NULL pointer dereference in 'brcmf_sdiod_sglist_rw'

Message ID 20241105204011.1603148-1-norbert.vanbolhuis@ev-box.com
State New
Headers show
Series wifi: brcmfmac: Fix oops due to NULL pointer dereference in 'brcmf_sdiod_sglist_rw' | expand

Commit Message

Norbert van Bolhuis Nov. 5, 2024, 8:40 p.m. UTC 
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.
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcmsdh.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcmsdh.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcmsdh.c
index 17f6b33beabd..42d991d9f8cb 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcmsdh.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcmsdh.c
@@ -770,7 +770,7 @@  void brcmf_sdiod_sgtable_alloc(struct brcmf_sdio_dev *sdiodev)
 
 	nents = max_t(uint, BRCMF_DEFAULT_RXGLOM_SIZE,
 		      sdiodev->settings->bus.sdio.txglomsz);
-	nents += (nents >> 4) + 1;
+	nents *= 2;
 
 	WARN_ON(nents > sdiodev->max_segment_count);