eeh_handle_special_event() is called when an EEH event is detected but
can't be narrowed down to a specific PE. This function looks through
every PE to find one in an erroneous state, then calls the regular event
handler eeh_handle_normal_event() once it knows which PE has an error.
However, if eeh_handle_normal_event() found that the PE cannot possibly
be recovered, it will remove the PE and associated devices. This leads
to a use after free in eeh_handle_special_event() as it attempts to clear
the "recovering" state on the PE after eeh_handle_normal_event() returns.
Thus, make sure the PE is valid when attempting to clear state in
eeh_handle_special_event().
Cc: <sta...@vger.kernel.org> #3.10+
Reported-by: Alexey Kardashevskiy <a...@ozlabs.ru>
Signed-off-by: Russell Currey <rus...@russell.cc>
---
arch/powerpc/kernel/eeh_driver.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
index b94887165a10..492397298a2a 100644
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -983,6 +983,19 @@ static void eeh_handle_special_event(void)
if (rc == EEH_NEXT_ERR_FROZEN_PE ||
rc == EEH_NEXT_ERR_FENCED_PHB) {
eeh_handle_normal_event(pe);
+
+ /*
+ * eeh_handle_normal_event() can free the PE if it
+ * determines that the PE cannot possibly be recovered.
+ * Make sure the PE still exists before changing its
+ * state.
+ */
+ if (!pe || (pe->type & EEH_PE_INVALID)
+ || (pe->state & EEH_PE_REMOVED)) {
+ pr_warn("EEH: not clearing state on bad PE\n");
+ continue;
+ }
+
eeh_pe_state_clear(pe, EEH_PE_RECOVERING);
} else {
pci_lock_rescan_remove();
--
2.12.0
