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| author | Alexander Bulekov <alxndr@bu.edu> | 2023-05-01 10:19:56 -0400 |
|---|---|---|
| committer | Michael Tokarev <mjt@tls.msk.ru> | 2023-09-10 19:38:01 +0300 |
| commit | 6a33d4b3453b46ee3fd432d80374f45919985b00 (patch) | |
| tree | 9fe60845c2d14ab1f49447880c8764f23c7c4f6f | |
| parent | 932cf49f0620544d1fb37f1d8dd02219a3636ee9 (diff) | |
| download | qemu-6a33d4b3453b46ee3fd432d80374f45919985b00.zip qemu-6a33d4b3453b46ee3fd432d80374f45919985b00.tar.gz qemu-6a33d4b3453b46ee3fd432d80374f45919985b00.tar.bz2 | |
async: avoid use-after-free on re-entrancy guard
A BH callback can free the BH, causing a use-after-free in aio_bh_call.
Fix that by keeping a local copy of the re-entrancy guard pointer.
Buglink: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=58513
Fixes: 9c86c97f12 ("async: Add an optional reentrancy guard to the BH API")
Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20230501141956.3444868-1-alxndr@bu.edu>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit 7915bd06f25e1803778081161bf6fa10c42dc7cd)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
| -rw-r--r-- | util/async.c | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/util/async.c b/util/async.c index 9df7674..055070f 100644 --- a/util/async.c +++ b/util/async.c @@ -156,18 +156,20 @@ void aio_bh_call(QEMUBH *bh) { bool last_engaged_in_io = false; - if (bh->reentrancy_guard) { - last_engaged_in_io = bh->reentrancy_guard->engaged_in_io; - if (bh->reentrancy_guard->engaged_in_io) { + /* Make a copy of the guard-pointer as cb may free the bh */ + MemReentrancyGuard *reentrancy_guard = bh->reentrancy_guard; + if (reentrancy_guard) { + last_engaged_in_io = reentrancy_guard->engaged_in_io; + if (reentrancy_guard->engaged_in_io) { trace_reentrant_aio(bh->ctx, bh->name); } - bh->reentrancy_guard->engaged_in_io = true; + reentrancy_guard->engaged_in_io = true; } bh->cb(bh->opaque); - if (bh->reentrancy_guard) { - bh->reentrancy_guard->engaged_in_io = last_engaged_in_io; + if (reentrancy_guard) { + reentrancy_guard->engaged_in_io = last_engaged_in_io; } } |