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([2601:647:4700:9b2:25da:dbcf:1e8c:d224]) by smtp.gmail.com with ESMTPSA id b21sm10316523pfp.172.2020.07.31.09.00.30 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 31 Jul 2020 09:00:30 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.1\)) Subject: Re: [PATCH kvm-unit-tests] fw_cfg: avoid index out of bounds From: Nadav Amit In-Reply-To: <20200730215809.1970-1-pbonzini@redhat.com> Date: Fri, 31 Jul 2020 09:00:29 -0700 Cc: kvm@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20200730215809.1970-1-pbonzini@redhat.com> To: Paolo Bonzini X-Mailer: Apple Mail (2.3608.120.23.2.1) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org >=20 > On Jul 30, 2020, at 2:58 PM, Paolo Bonzini = wrote: >=20 > clang compilation fails with >=20 > lib/x86/fwcfg.c:32:3: error: array index 17 is past the end of the = array (which contains 16 elements) [-Werror,-Warray-bounds] > fw_override[FW_CFG_MAX_RAM] =3D atol(str) * 1024 * = 1024; >=20 > The reason is that FW_CFG_MAX_RAM does not exist in the fw-cfg spec = and was > added for bare metal support. Fix the size of the array and rename = FW_CFG_MAX_ENTRY > to FW_CFG_NUM_ENTRIES, so that it is clear that it must be one plus = the > highest valid entry. >=20 > Signed-off-by: Paolo Bonzini > --- > lib/x86/fwcfg.c | 6 +++--- > lib/x86/fwcfg.h | 5 ++++- > 2 files changed, 7 insertions(+), 4 deletions(-) >=20 > diff --git a/lib/x86/fwcfg.c b/lib/x86/fwcfg.c > index c2aaf5a..1734afb 100644 > --- a/lib/x86/fwcfg.c > +++ b/lib/x86/fwcfg.c > @@ -4,7 +4,7 @@ >=20 > static struct spinlock lock; >=20 > -static long fw_override[FW_CFG_MAX_ENTRY]; > +static long fw_override[FW_CFG_NUM_ENTRIES]; > static bool fw_override_done; >=20 > bool no_test_device; > @@ -15,7 +15,7 @@ static void read_cfg_override(void) > int i; >=20 > /* Initialize to negative value that would be considered as = invalid */ > - for (i =3D 0; i < FW_CFG_MAX_ENTRY; i++) > + for (i =3D 0; i < FW_CFG_NUM_ENTRIES; i++) > fw_override[i] =3D -1; >=20 > if ((str =3D getenv("NR_CPUS"))) > @@ -44,7 +44,7 @@ static uint64_t fwcfg_get_u(uint16_t index, int = bytes) > if (!fw_override_done) > read_cfg_override(); >=20 > - if (index < FW_CFG_MAX_ENTRY && fw_override[index] >=3D 0) > + if (index < FW_CFG_NUM_ENTRIES && fw_override[index] >=3D 0) > return fw_override[index]; >=20 > spin_lock(&lock); > diff --git a/lib/x86/fwcfg.h b/lib/x86/fwcfg.h > index 64d4c6e..ac4257e 100644 > --- a/lib/x86/fwcfg.h > +++ b/lib/x86/fwcfg.h > @@ -20,9 +20,12 @@ > #define FW_CFG_NUMA 0x0d > #define FW_CFG_BOOT_MENU 0x0e > #define FW_CFG_MAX_CPUS 0x0f > -#define FW_CFG_MAX_ENTRY 0x10 > + > +/* Dummy entries used when running on bare metal */ > #define FW_CFG_MAX_RAM 0x11 >=20 > +#define FW_CFG_NUM_ENTRIES (FW_CFG_MAX_RAM + 1) > + > #define FW_CFG_WRITE_CHANNEL 0x4000 > #define FW_CFG_ARCH_LOCAL 0x8000 > #define FW_CFG_ENTRY_MASK ~(FW_CFG_WRITE_CHANNEL | = FW_CFG_ARCH_LOCAL) > =E2=80=94=20 > 2.26.2 For the record: I did send a patch more than two weeks ago to fix this problem (that I created).