| Message ID | 20231215120307.545381-1-jcmvbkbc@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | target/xtensa: fix OOB TLB entry access | expand |
On Fri, 15 Dec 2023 at 12:05, Max Filippov <jcmvbkbc@gmail.com> wrote: > > r[id]tlb[01], [iw][id]tlb opcodes use TLB way index passed in a register > by the guest. The host uses 3 bits of the index for ITLB indexing and 4 > bits for DTLB, but there's only 7 entries in the ITLB array and 10 in > the DTLB array, so a malicious guest may trigger out-of-bound access to > these arrays. > > Change split_tlb_entry_spec return type to bool to indicate whether TLB > way passed to it is valid. Change get_tlb_entry to return NULL in case > invalid TLB way is requested. Add assertion to xtensa_tlb_get_entry that > requested TLB way and entry indices are valid. Add checks to the > [rwi]tlb helpers that requested TLB way is valid and return 0 or do > nothing when it's not. > > Cc: qemu-stable@nongnu.org > Fixes: b67ea0cd7441 ("target-xtensa: implement memory protection options") > Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> > --- Reviewed-by: Peter Maydell <peter.maydell@linaro.org> thanks -- PMM
15.12.2023 15:03, Max Filippov : > r[id]tlb[01], [iw][id]tlb opcodes use TLB way index passed in a register > by the guest. The host uses 3 bits of the index for ITLB indexing and 4 > bits for DTLB, but there's only 7 entries in the ITLB array and 10 in > the DTLB array, so a malicious guest may trigger out-of-bound access to > these arrays. > > Change split_tlb_entry_spec return type to bool to indicate whether TLB > way passed to it is valid. Change get_tlb_entry to return NULL in case > invalid TLB way is requested. Add assertion to xtensa_tlb_get_entry that > requested TLB way and entry indices are valid. Add checks to the > [rwi]tlb helpers that requested TLB way is valid and return 0 or do > nothing when it's not. > > Cc: qemu-stable@nongnu.org > Fixes: b67ea0cd7441 ("target-xtensa: implement memory protection options") > Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> Ping? Can we get this to master before Jan-27? :) Thanks, /mjt
On Thu, 18 Jan 2024 at 08:01, Michael Tokarev <mjt@tls.msk.ru> wrote: > > 15.12.2023 15:03, Max Filippov : > > r[id]tlb[01], [iw][id]tlb opcodes use TLB way index passed in a register > > by the guest. The host uses 3 bits of the index for ITLB indexing and 4 > > bits for DTLB, but there's only 7 entries in the ITLB array and 10 in > > the DTLB array, so a malicious guest may trigger out-of-bound access to > > these arrays. > > > > Change split_tlb_entry_spec return type to bool to indicate whether TLB > > way passed to it is valid. Change get_tlb_entry to return NULL in case > > invalid TLB way is requested. Add assertion to xtensa_tlb_get_entry that > > requested TLB way and entry indices are valid. Add checks to the > > [rwi]tlb helpers that requested TLB way is valid and return 0 or do > > nothing when it's not. > > > > Cc: qemu-stable@nongnu.org > > Fixes: b67ea0cd7441 ("target-xtensa: implement memory protection options") > > Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> > > Ping? > Can we get this to master before Jan-27? :) I can take it via target-arm.next, I guess. -- PMM
diff --git a/target/xtensa/mmu_helper.c b/target/xtensa/mmu_helper.c index 12552a33470e..2fda4e887cce 100644 --- a/target/xtensa/mmu_helper.c +++ b/target/xtensa/mmu_helper.c @@ -224,22 +224,31 @@ static void split_tlb_entry_spec_way(const CPUXtensaState *env, uint32_t v, * Split TLB address into TLB way, entry index and VPN (with index). * See ISA, 4.6.5.5 - 4.6.5.8 for the TLB addressing format */ -static void split_tlb_entry_spec(CPUXtensaState *env, uint32_t v, bool dtlb, - uint32_t *vpn, uint32_t *wi, uint32_t *ei) +static bool split_tlb_entry_spec(CPUXtensaState *env, uint32_t v, bool dtlb, + uint32_t *vpn, uint32_t *wi, uint32_t *ei) { if (xtensa_option_enabled(env->config, XTENSA_OPTION_MMU)) { *wi = v & (dtlb ? 0xf : 0x7); - split_tlb_entry_spec_way(env, v, dtlb, vpn, *wi, ei); + if (*wi < (dtlb ? env->config->dtlb.nways : env->config->itlb.nways)) { + split_tlb_entry_spec_way(env, v, dtlb, vpn, *wi, ei); + return true; + } else { + return false; + } } else { *vpn = v & REGION_PAGE_MASK; *wi = 0; *ei = (v >> 29) & 0x7; + return true; } } static xtensa_tlb_entry *xtensa_tlb_get_entry(CPUXtensaState *env, bool dtlb, unsigned wi, unsigned ei) { + const xtensa_tlb *tlb = dtlb ? &env->config->dtlb : &env->config->itlb; + + assert(wi < tlb->nways && ei < tlb->way_size[wi]); return dtlb ? env->dtlb[wi] + ei : env->itlb[wi] + ei; @@ -252,11 +261,14 @@ static xtensa_tlb_entry *get_tlb_entry(CPUXtensaState *env, uint32_t wi; uint32_t ei; - split_tlb_entry_spec(env, v, dtlb, &vpn, &wi, &ei); - if (pwi) { - *pwi = wi; + if (split_tlb_entry_spec(env, v, dtlb, &vpn, &wi, &ei)) { + if (pwi) { + *pwi = wi; + } + return xtensa_tlb_get_entry(env, dtlb, wi, ei); + } else { + return NULL; } - return xtensa_tlb_get_entry(env, dtlb, wi, ei); } static void xtensa_tlb_set_entry_mmu(const CPUXtensaState *env, @@ -482,7 +494,12 @@ uint32_t HELPER(rtlb0)(CPUXtensaState *env, uint32_t v, uint32_t dtlb) if (xtensa_option_enabled(env->config, XTENSA_OPTION_MMU)) { uint32_t wi; const xtensa_tlb_entry *entry = get_tlb_entry(env, v, dtlb, &wi); - return (entry->vaddr & get_vpn_mask(env, dtlb, wi)) | entry->asid; + + if (entry) { + return (entry->vaddr & get_vpn_mask(env, dtlb, wi)) | entry->asid; + } else { + return 0; + } } else { return v & REGION_PAGE_MASK; } @@ -491,7 +508,12 @@ uint32_t HELPER(rtlb0)(CPUXtensaState *env, uint32_t v, uint32_t dtlb) uint32_t HELPER(rtlb1)(CPUXtensaState *env, uint32_t v, uint32_t dtlb) { const xtensa_tlb_entry *entry = get_tlb_entry(env, v, dtlb, NULL); - return entry->paddr | entry->attr; + + if (entry) { + return entry->paddr | entry->attr; + } else { + return 0; + } } void HELPER(itlb)(CPUXtensaState *env, uint32_t v, uint32_t dtlb) @@ -499,7 +521,7 @@ void HELPER(itlb)(CPUXtensaState *env, uint32_t v, uint32_t dtlb) if (xtensa_option_enabled(env->config, XTENSA_OPTION_MMU)) { uint32_t wi; xtensa_tlb_entry *entry = get_tlb_entry(env, v, dtlb, &wi); - if (entry->variable && entry->asid) { + if (entry && entry->variable && entry->asid) { tlb_flush_page(env_cpu(env), entry->vaddr); entry->asid = 0; } @@ -537,8 +559,9 @@ void HELPER(wtlb)(CPUXtensaState *env, uint32_t p, uint32_t v, uint32_t dtlb) uint32_t vpn; uint32_t wi; uint32_t ei; - split_tlb_entry_spec(env, v, dtlb, &vpn, &wi, &ei); - xtensa_tlb_set_entry(env, dtlb, wi, ei, vpn, p); + if (split_tlb_entry_spec(env, v, dtlb, &vpn, &wi, &ei)) { + xtensa_tlb_set_entry(env, dtlb, wi, ei, vpn, p); + } } /*!
r[id]tlb[01], [iw][id]tlb opcodes use TLB way index passed in a register by the guest. The host uses 3 bits of the index for ITLB indexing and 4 bits for DTLB, but there's only 7 entries in the ITLB array and 10 in the DTLB array, so a malicious guest may trigger out-of-bound access to these arrays. Change split_tlb_entry_spec return type to bool to indicate whether TLB way passed to it is valid. Change get_tlb_entry to return NULL in case invalid TLB way is requested. Add assertion to xtensa_tlb_get_entry that requested TLB way and entry indices are valid. Add checks to the [rwi]tlb helpers that requested TLB way is valid and return 0 or do nothing when it's not. Cc: qemu-stable@nongnu.org Fixes: b67ea0cd7441 ("target-xtensa: implement memory protection options") Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> --- target/xtensa/mmu_helper.c | 47 ++++++++++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 12 deletions(-)