[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [qemu-xen stable-4.19] async: avoid use-after-free on re-entrancy guard
commit 6a33d4b3453b46ee3fd432d80374f45919985b00 Author: Alexander Bulekov <alxndr@xxxxxx> AuthorDate: Mon May 1 10:19:56 2023 -0400 Commit: Michael Tokarev <mjt@xxxxxxxxxx> CommitDate: Sun Sep 10 19:38:01 2023 +0300 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@xxxxxx> Message-Id: <20230501141956.3444868-1-alxndr@xxxxxx> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx> (cherry picked from commit 7915bd06f25e1803778081161bf6fa10c42dc7cd) Signed-off-by: Michael Tokarev <mjt@xxxxxxxxxx> --- util/async.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/util/async.c b/util/async.c index 9df7674b4e..055070ffbd 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; } } -- generated by git-patchbot for /home/xen/git/qemu-xen.git#stable-4.19
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