[PATCH] firewire: ohci: fix NULL pointer dereference in ar_context_release
"syzbot" <[email protected]>
| Newsgroups | gmane.linux.kernel,gmane.linux.kernel.firewire.devel |
|---|---|
| Message-ID | <[email protected]> |
From: Aleksandr Nogikh <[email protected]> During the error handling path of the driver's probe function, a NULL pointer dereference can occur in ar_context_release(). When pci_probe() fails early (e.g., if pcim_enable_device() or MMIO mapping fails), the devres cleanup mechanism invokes release_ohci(). This function unconditionally calls ar_context_release() to clean up the asynchronous receive contexts. However, if ar_context_init() was not yet called, ctx->ohci remains NULL (as the fw_ohci structure is zero-initialized by devres_alloc()). ar_context_release() immediately dereferences ctx->ohci to get the dev pointer before checking if the context was actually initialized, leading to a crash: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] RIP: 0010:ar_context_release+0x3f/0x380 drivers/firewire/ohci.c:543 Call Trace: release_ohci+0x3f/0x60 drivers/firewire/ohci.c:3567 release_nodes drivers/base/devres.c:546 [inline] devres_release_all+0x1a8/0x260 drivers/base/devres.c:576 device_unbind_cleanup drivers/base/dd.c:597 [inline] really_probe+0x451/0xae0 drivers/base/dd.c:772 To fix this, move the assignment of the dev pointer after the !ctx->buffer check. If ctx->buffer is NULL, it indicates that the context was never successfully initialized and there is nothing to release, safely avoiding the dereference of the uninitialized ctx->ohci pointer. Fixes: 5716e58aecdd ("firewire: ohci: release buffer for AR req/resp contexts when managed resource is released") Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot Reported-by: [email protected] Closes: https://syzkaller.appspot.com/bug?extid=d30aad27833a559defab Link: https://syzkaller.appspot.com/ai_job?id=10a18617-7893-42dd-bf1c-cd49e19e95d9 Signed-off-by: Aleksandr Nogikh <[email protected]> --- diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c index 8153d62c5..e947227e0 100644 --- a/drivers/firewire/ohci.c +++ b/drivers/firewire/ohci.c @@ -540,11 +540,13 @@ static void ar_context_link_page(struct ar_context *ctx, unsigned int index) static void ar_context_release(struct ar_context *ctx) { - struct device *dev = ctx->ohci->card.device; + struct device *dev; if (!ctx->buffer) return; + dev = ctx->ohci->card.device; + for (int i = 0; i < AR_BUFFERS; ++i) { dma_addr_t dma_addr = ctx->dma_addrs[i]; if (dma_addr) base-commit: 075b74841bd0065a3bda3440873c747938e69b68 -- See https://goo.gle/syzbot-ai-patches for information about AI-generated patches. The person who has signed off on the patch is responsible for addressing comments. syzbot engineers can be reached at [email protected].