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72 lines
2.5 KiB
72 lines
2.5 KiB
9 months ago
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From d754050d260e2ad890cecd975df6e163c531b40e Mon Sep 17 00:00:00 2001
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From: Jon Maloy <jmaloy@redhat.com>
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Date: Tue, 9 May 2023 10:29:03 -0400
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Subject: [PATCH 09/15] async: avoid use-after-free on re-entrancy guard
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RH-Author: Jon Maloy <jmaloy@redhat.com>
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RH-MergeRequest: 277: memory: prevent dma-reentracy issues
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RH-Bugzilla: 1999236
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [9/12] d357650e581c3921bbfe3e2fde5e3f55853b5fab (redhat/rhel/src/qemu-kvm/jons-qemu-kvm-2)
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1999236
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Upstream: Merged
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CVE: CVE-2021-3750
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commit 7915bd06f25e1803778081161bf6fa10c42dc7cd
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Author: Alexander Bulekov <alxndr@bu.edu>
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Date: Mon May 1 10:19:56 2023 -0400
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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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Signed-off-by: Jon Maloy <jmaloy@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 1fff02e7fc..ffe0541c3b 100644
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--- a/util/async.c
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+++ b/util/async.c
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@@ -146,18 +146,20 @@ 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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2.37.3
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