53 lines
1.8 KiB
Diff
53 lines
1.8 KiB
Diff
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From b2b00599451de0c9fe4dcdf7c47fb1d585ab7d23 Mon Sep 17 00:00:00 2001
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From: Alexander Bulekov <alxndr@bu.edu>
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Date: Mon, 1 May 2023 10:19:56 -0400
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Subject: [PATCH] async: avoid use-after-free on re-entrancy guard
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A BH callback can free the BH, causing a use-after-free in aio_bh_call.
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Fix that by keeping a local copy of the re-entrancy guard pointer.
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Buglink: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=58513
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Fixes: 9c86c97f12 ("async: Add an optional reentrancy guard to the BH API")
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Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
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Message-Id: <20230501141956.3444868-1-alxndr@bu.edu>
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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---
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util/async.c | 14 ++++++++------
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1 file changed, 8 insertions(+), 6 deletions(-)
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diff --git a/util/async.c b/util/async.c
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index 3eb6b50163..760ad73404 100644
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--- a/util/async.c
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+++ b/util/async.c
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@@ -142,18 +142,20 @@ void aio_bh_call(QEMUBH *bh)
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{
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bool last_engaged_in_io = false;
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- if (bh->reentrancy_guard) {
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- last_engaged_in_io = bh->reentrancy_guard->engaged_in_io;
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- if (bh->reentrancy_guard->engaged_in_io) {
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+ /* Make a copy of the guard-pointer as cb may free the bh */
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+ MemReentrancyGuard *reentrancy_guard = bh->reentrancy_guard;
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+ if (reentrancy_guard) {
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+ last_engaged_in_io = reentrancy_guard->engaged_in_io;
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+ if (reentrancy_guard->engaged_in_io) {
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trace_reentrant_aio(bh->ctx, bh->name);
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}
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- bh->reentrancy_guard->engaged_in_io = true;
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+ reentrancy_guard->engaged_in_io = true;
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}
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bh->cb(bh->opaque);
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- if (bh->reentrancy_guard) {
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- bh->reentrancy_guard->engaged_in_io = last_engaged_in_io;
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+ if (reentrancy_guard) {
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+ reentrancy_guard->engaged_in_io = last_engaged_in_io;
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}
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}
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--
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2.27.0
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