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d="scan'208";a="52741153" From: Andrew Cooper To: Xen-devel CC: Andrew Cooper , George Dunlap , Ian Jackson , Jan Beulich , Stefano Stabellini , Wei Liu , Julien Grall , Dario Faggioli , Meng Xu Subject: [PATCH v2 01/12] xen/trace: Don't over-read trace objects Date: Mon, 20 Sep 2021 18:25:18 +0100 Message-ID: <20210920172529.24932-2-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20210920172529.24932-1-andrew.cooper3@citrix.com> References: <20210920172529.24932-1-andrew.cooper3@citrix.com> MIME-Version: 1.0 Content-Type: text/plain In the case that 'extra' isn't a multiple of uint32_t, the calculation rounds the number of bytes up, causing later logic to read unrelated bytes beyond the end of the object. Also, asserting that the object is within TRACE_EXTRA_MAX, but truncating it in release builds is rude. Instead, reject any out-of-spec records, leaving enough of a message to identify the faulty caller. There is one buggy race record, TRC_RTDS_BUDGET_BURN. As it must remain __packed (as cur_budget is misaligned), change bool has_extratime to uint32_t to compensate. The new printk() can also be hit by HVMOP_xentrace, although no over-read is possible. This has no business being a hypercall in the first place, as it can't be used outside of custom local debugging, so extend the uint32_t requirement to HVMOP_xentrace too. Signed-off-by: Andrew Cooper --- CC: George Dunlap CC: Ian Jackson CC: Jan Beulich CC: Stefano Stabellini CC: Wei Liu CC: Julien Grall CC: Dario Faggioli CC: Meng Xu v2: * Adjust HVMOP_xentrace to avoid hitting the printk() * Fix TRC_RTDS_BUDGET_BURN * Adjust wording in __trace_var() --- xen/arch/x86/hvm/hvm.c | 5 +++-- xen/common/sched/rt.c | 24 +++++++++++++----------- xen/common/trace.c | 21 ++++++++++----------- 3 files changed, 26 insertions(+), 24 deletions(-) diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index 7b48a1b925bb..09cf6330ad26 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -5063,8 +5063,9 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg) if ( copy_from_guest(&tr, arg, 1 ) ) return -EFAULT; - if ( tr.extra_bytes > sizeof(tr.extra) - || (tr.event & ~((1u< sizeof(tr.extra) || + tr.event >> TRC_SUBCLS_SHIFT ) return -EINVAL; /* Cycles will be taken at the vmexit and vmenter */ diff --git a/xen/common/sched/rt.c b/xen/common/sched/rt.c index c24cd2ac3200..c58edca0de84 100644 --- a/xen/common/sched/rt.c +++ b/xen/common/sched/rt.c @@ -968,18 +968,20 @@ burn_budget(const struct scheduler *ops, struct rt_unit *svc, s_time_t now) /* TRACE */ { struct __packed { - unsigned unit:16, dom:16; + uint16_t unit, dom; uint64_t cur_budget; - int delta; - unsigned priority_level; - bool has_extratime; - } d; - d.dom = svc->unit->domain->domain_id; - d.unit = svc->unit->unit_id; - d.cur_budget = (uint64_t) svc->cur_budget; - d.delta = delta; - d.priority_level = svc->priority_level; - d.has_extratime = svc->flags & RTDS_extratime; + uint32_t delta; + uint32_t priority_level; + uint32_t has_extratime; + } d = { + .unit = svc->unit->unit_id, + .dom = svc->unit->domain->domain_id, + .cur_budget = svc->cur_budget, + .delta = delta, + .priority_level = svc->priority_level, + .has_extratime = !!(svc->flags & RTDS_extratime), + }; + trace_var(TRC_RTDS_BUDGET_BURN, 1, sizeof(d), (unsigned char *) &d); diff --git a/xen/common/trace.c b/xen/common/trace.c index a2a389a1c7c3..4297ff505fb9 100644 --- a/xen/common/trace.c +++ b/xen/common/trace.c @@ -686,22 +686,21 @@ void __trace_var(u32 event, bool_t cycles, unsigned int extra, unsigned long flags; u32 bytes_to_tail, bytes_to_wrap; unsigned int rec_size, total_size; - unsigned int extra_word; bool_t started_below_highwater; if( !tb_init_done ) return; - /* Convert byte count into word count, rounding up */ - extra_word = (extra / sizeof(u32)); - if ( (extra % sizeof(u32)) != 0 ) - extra_word++; - - ASSERT(extra_word <= TRACE_EXTRA_MAX); - extra_word = min_t(int, extra_word, TRACE_EXTRA_MAX); - - /* Round size up to nearest word */ - extra = extra_word * sizeof(u32); + /* + * extra data needs to be an exact multiple of uint32_t to prevent the + * later logic over-reading the object. Reject out-of-spec records. Any + * failure here is an error in the caller. + */ + if ( extra % sizeof(uint32_t) || + extra / sizeof(uint32_t) > TRACE_EXTRA_MAX ) + return printk_once(XENLOG_WARNING + "Trace event %#x bad size %u, discarding\n", + event, extra); if ( (tb_event_mask & event) == 0 ) return; -- 2.11.0