Messages in this thread | | | Date | Mon, 15 Nov 2021 17:27:22 -0800 | From | Jakub Kicinski <> | Subject | Re: [PATCH] net: dpaa2-eth: fix use-after-free in dpaa2_eth_remove |
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On Mon, 15 Nov 2021 11:08:17 +0300 Dan Carpenter wrote: > > @Dan, is there a smatch checker for straigthforward use after free bugs? > > Like acessing pointer after free was called? I think, adding > > free_netdev() to check list might be good idea > > > > I've skimmed througth smatch source and didn't find one, so can you, > > please, point out to it if it exists. > > It's check_free_strict.c. > > It does cross function analysis but free_netdev() is tricky because it > doesn't free directly, it just drops the reference count. Also it > delays freeing in the NETREG_UNREGISTERING path so this check might > cause false positives?
I'd ignore that path, it's just special casing that's supposed to keep the driver-visible API sane. Nobody should be touching netdev past free_netdev(). Actually if you can it'd be interesting to add checks for using whatever netdev_priv(ndev) returned past free_netdev(ndev).
Most UAFs that come to mind from the past were people doing something like:
struct my_priv *mine = netdev_priv(ndev);
netdev_unregister(ndev); free_netdev(ndev);
free(mine->bla); /* UAF, free_netdev() frees the priv */
> I'll add free_netdev() to the list of free > functions and test it overnight tonight. > > register_free_hook("free_netdev", &match_free, 0);
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