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[v2,21/23] x86: Allow get_locked_pte() to fail

Message ID b7fa8547-4f28-ec82-9893-1b2eb58e40b4@google.com (mailing list archive)
State New, archived
Headers show
Series arch: allow pte_offset_map[_lock]() to fail | expand

Commit Message

Hugh Dickins June 8, 2023, 7:35 p.m. UTC 
In rare transient cases, not yet made possible, pte_offset_map() and
pte_offset_map_lock() may not find a page table: handle appropriately.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
 arch/x86/kernel/ldt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
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Patch

diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index 525876e7b9f4..adc67f98819a 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -367,8 +367,10 @@  static void unmap_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt)
 
 		va = (unsigned long)ldt_slot_va(ldt->slot) + offset;
 		ptep = get_locked_pte(mm, va, &ptl);
-		pte_clear(mm, va, ptep);
-		pte_unmap_unlock(ptep, ptl);
+		if (!WARN_ON_ONCE(!ptep)) {
+			pte_clear(mm, va, ptep);
+			pte_unmap_unlock(ptep, ptl);
+		}
 	}
 
 	va = (unsigned long)ldt_slot_va(ldt->slot);