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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774969453; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3F5JMu/lV41yfl1mxCaocZma8j3FtqQndeH67Sr02Ms=; b=cpyVmNGHWtkEHpxeAeZ2LGb6e6xEESLwvK1LhVO9jsa9Fv1NYj1xuNOx9PMmdGjNd3LxZi CGxl935CP+qbfj/Xe1t1Lry2wSwV4Iz3uIHKxCOoweIdHKqmTZs1L7OT2Vjc3jhFUTqCmX 0Vwk/OjkcoWhsL2q/Y8xrOrgcVpu3J0= X-MC-Unique: UIT-HEXEPwq60rURQK4aFg-1 X-Mimecast-MFC-AGG-ID: UIT-HEXEPwq60rURQK4aFg_1774969448 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org, peter.maydell@linaro.org Subject: [PULL 6/6] block: Fix crash after setting latency historygram with single bin Date: Tue, 31 Mar 2026 17:03:52 +0200 Message-ID: <20260331150352.256332-7-kwolf@redhat.com> In-Reply-To: <20260331150352.256332-1-kwolf@redhat.com> References: <20260331150352.256332-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" Passing an empty list of boundaries to block-latency-histogram-set sets up a state that leads to a NULL pointer dereference when the next request should be accounted for. This is not a useful configuration, so just error out if the user tries to set it. The crash can easily be reproduced with the following script: qmp() { cat < Message-ID: <20260331102608.60882-1-kwolf@redhat.com> Signed-off-by: Kevin Wolf --- block/accounting.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/block/accounting.c b/block/accounting.c index 5cf51f029b1..f00fe997403 100644 --- a/block/accounting.c +++ b/block/accounting.c @@ -185,6 +185,15 @@ int block_latency_histogram_set(BlockAcctStats *stats,= enum BlockAcctType type, prev =3D entry->value; } =20 + /* + * block_latency_histogram_account() assumes that it can always access + * hist->boundaries[0], so require at least one boundary. A histogram = with + * a single bin is useless anyway. + */ + if (new_nbins <=3D 1) { + return -EINVAL; + } + hist->nbins =3D new_nbins; g_free(hist->boundaries); hist->boundaries =3D g_new(uint64_t, hist->nbins - 1); --=20 2.53.0