linux-kernel - [PATCH] powerpc/mm: fix mmap

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Date:   Mon,  6 Mar 2023 14:55:20 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, Sachin Sant <sachinp@...ux.ibm.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH] powerpc/mm: fix mmap_lock bad unlock

When page fault is tried holding the per VMA lock, bad_access_pkey() and
bad_access() should not be called because it is assuming the mmap_lock is
held.
In the case a bad access is detected, fall back to the default path,
grabbing the mmap_lock to handle the fault and report the error.

Fixes: 169db3bb4609 ("powerc/mm: try VMA lock-based page fault handling first")
Reported-by: Sachin Sant <sachinp@...ux.ibm.com>
Link: https://lore.kernel.org/linux-mm/842502FB-F99C-417C-9648-A37D0ECDC9CE@linux.ibm.com
Cc: Suren Baghdasaryan <surenb@...gle.com>
Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
 arch/powerpc/mm/fault.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index c7ae86b04b8a..e191b3ebd8d6 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -479,17 +479,13 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
 
 	if (unlikely(access_pkey_error(is_write, is_exec,
 				       (error_code & DSISR_KEYFAULT), vma))) {
-		int rc = bad_access_pkey(regs, address, vma);
-
 		vma_end_read(vma);
-		return rc;
+		goto lock_mmap;
 	}
 
 	if (unlikely(access_error(is_write, is_exec, vma))) {
-		int rc = bad_access(regs, address);
-
 		vma_end_read(vma);
-		return rc;
+		goto lock_mmap;
 	}
 
 	fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
-- 
2.39.2