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Message-ID: <20230708191212.4147700-1-surenb@google.com>
Date: Sat, 8 Jul 2023 12:12:10 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: torvalds@...ux-foundation.org
Cc: akpm@...ux-foundation.org, regressions@...mhuis.info,
bagasdotme@...il.com, jacobly.alt@...il.com, willy@...radead.org,
liam.howlett@...cle.com, david@...hat.com, peterx@...hat.com,
ldufour@...ux.ibm.com, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
linux-arm-kernel@...ts.infradead.org, gregkh@...uxfoundation.org,
regressions@...ts.linux.dev,
Suren Baghdasaryan <surenb@...gle.com>, stable@...r.kernel.org
Subject: [PATCH v2 1/3] mm: lock a vma before stack expansion
With recent changes necessitating mmap_lock to be held for write while
expanding a stack, per-VMA locks should follow the same rules and be
write-locked to prevent page faults into the VMA being expanded. Add
the necessary locking.
Cc: stable@...r.kernel.org
Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
mm/mmap.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/mm/mmap.c b/mm/mmap.c
index 204ddcd52625..c66e4622a557 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1977,6 +1977,8 @@ static int expand_upwards(struct vm_area_struct *vma, unsigned long address)
return -ENOMEM;
}
+ /* Lock the VMA before expanding to prevent concurrent page faults */
+ vma_start_write(vma);
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_lock in read mode. We need the
@@ -2064,6 +2066,8 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address)
return -ENOMEM;
}
+ /* Lock the VMA before expanding to prevent concurrent page faults */
+ vma_start_write(vma);
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_lock in read mode. We need the
--
2.41.0.390.g38632f3daf-goog
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