From: James Morse james.morse@arm.com
commit 1e72e673b9d102ff2e8333e74b3308d012ddf75b upstream.
ghes_edac models a single logical memory controller, and uses a global ghes_init variable to ensure only the first ghes_edac_register() will do anything.
ghes_edac is registered the first time a GHES entry in the HEST is probed. There may be multiple entries, so subsequent attempts to register ghes_edac are silently ignored as the work has already been done.
When a GHES entry is unregistered, it calls ghes_edac_unregister(), which free()s the memory behind the global variables in ghes_edac.
But there may be multiple GHES entries, the next call to ghes_edac_unregister() will dereference the free()d memory, and attempt to free it a second time.
This may also be triggered on a platform with one GHES entry, if the driver is unbound/re-bound and unbound. The re-bind step will do nothing because of ghes_init, the second unbind will then do the same work as the first.
Doing the unregister work on the first call is unsafe, as another CPU may be processing a notification in ghes_edac_report_mem_error(), using the memory we are about to free.
ghes_init is already half of the reference counting. We only need to do the register work for the first call, and the unregister work for the last. Add the unregister check.
This means we no longer free ghes_edac's memory while there are GHES entries that may receive a notification.
This was detected by KASAN and DEBUG_TEST_DRIVER_REMOVE.
[ bp: merge into a single patch. ]
Fixes: 0fe5f281f749 ("EDAC, ghes: Model a single, logical memory controller") Reported-by: John Garry john.garry@huawei.com Signed-off-by: James Morse james.morse@arm.com Signed-off-by: Borislav Petkov bp@suse.de Cc: linux-edac linux-edac@vger.kernel.org Cc: Mauro Carvalho Chehab mchehab@kernel.org Cc: Robert Richter rrichter@marvell.com Cc: Tony Luck tony.luck@intel.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20191014171919.85044-2-james.morse@arm.com Link: https://lkml.kernel.org/r/304df85b-8b56-b77e-1a11-aa23769f2e7c@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/edac/ghes_edac.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/edac/ghes_edac.c +++ b/drivers/edac/ghes_edac.c @@ -532,7 +532,11 @@ void ghes_edac_unregister(struct ghes *g if (!ghes_pvt) return;
+ if (atomic_dec_return(&ghes_init)) + return; + mci = ghes_pvt->mci; + ghes_pvt = NULL; edac_mc_del_mc(mci->pdev); edac_mc_free(mci); }