powerpc/32: Fix hardlockup on vmap stack overflow
authorChristophe Leroy <christophe.leroy@csgroup.eu>
Thu, 18 Nov 2021 09:39:53 +0000 (10:39 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 1 Dec 2021 08:19:01 +0000 (09:19 +0100)
commit 5bb60ea611db1e04814426ed4bd1c95d1487678e upstream.

Since the commit c118c7303ad5 ("powerpc/32: Fix vmap stack - Do not
activate MMU before reading task struct") a vmap stack overflow
results in a hard lockup. This is because emergency_ctx is still
addressed with its virtual address allthough data MMU is not active
anymore at that time.

Fix it by using a physical address instead.

Fixes: c118c7303ad5 ("powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct")
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/ce30364fb7ccda489272af4a1612b6aa147e1d23.1637227521.git.christophe.leroy@csgroup.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/powerpc/kernel/head_32.h

index f8e3d15ddf694c0cfc72c148174016716dc1807e..abb057a86739b791c6fa8c50f8d8fa850b6e2543 100644 (file)
@@ -333,11 +333,11 @@ label:
        mfspr   r1, SPRN_SPRG_THREAD
        lwz     r1, TASK_CPU - THREAD(r1)
        slwi    r1, r1, 3
-       addis   r1, r1, emergency_ctx@ha
+       addis   r1, r1, emergency_ctx-PAGE_OFFSET@ha
 #else
-       lis     r1, emergency_ctx@ha
+       lis     r1, emergency_ctx-PAGE_OFFSET@ha
 #endif
-       lwz     r1, emergency_ctx@l(r1)
+       lwz     r1, emergency_ctx-PAGE_OFFSET@l(r1)
        addi    r1, r1, THREAD_SIZE - INT_FRAME_SIZE
        EXCEPTION_PROLOG_2
        SAVE_NVGPRS(r11)