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| author |   Nadav Amit <namit@cs.technion.ac.il> | 2014-11-19 17:43:09 +0200 |
|---|---|---|
| committer |   Paolo Bonzini <pbonzini@redhat.com> | 2014-11-19 18:17:10 +0100 |
| commit | 1c1c35ae4b75d6fc08393a1f73a5a06dc68eebb8 (patch) | |
| tree | f8a03ce263b63e50c06266415b193785f5a1ce1a /arch/x86/kvm | |
| parent | KVM: x86: Revert NoBigReal patch in the emulator (diff) | |
| download | linux-dev-1c1c35ae4b75d6fc08393a1f73a5a06dc68eebb8.tar.xz linux-dev-1c1c35ae4b75d6fc08393a1f73a5a06dc68eebb8.zip | |
KVM: x86: Stack size is overridden by __linearize
When performing segmented-read/write in the emulator for stack operations, it
ignores the stack size, and uses the ad_bytes as indication for the pointer
size. As a result, a wrong address may be accessed.
To fix this behavior, we can remove the masking of address in __linearize and
perform it beforehand. It is already done for the operands (so currently it is
inefficiently done twice). It is missing in two cases:
1. When using rip_relative
2. On fetch_bit_operand that changes the address.
This patch masks the address on these two occassions, and removes the masking
from __linearize.
Note that it does not mask EIP during fetch. In protected/legacy mode code
fetch when RIP >= 2^32 should result in #GP and not wrap-around. Since we make
limit checks within __linearize, this is the expected behavior.
Partial revert of commit 518547b32ab4 (KVM: x86: Emulator does not
calculate address correctly, 2014-09-30).
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 5d47714d895d..1317560d0823 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -665,8 +665,7 @@ static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt, u16 sel; unsigned cpl; - la = seg_base(ctxt, addr.seg) + - (fetch || ctxt->ad_bytes == 8 ? addr.ea : (u32)addr.ea); + la = seg_base(ctxt, addr.seg) + addr.ea; *max_size = 0; switch (ctxt->mode) { case X86EMUL_MODE_PROT64: @@ -1289,7 +1288,8 @@ static void fetch_bit_operand(struct x86_emulate_ctxt *ctxt) else sv = (s64)ctxt->src.val & (s64)mask; - ctxt->dst.addr.mem.ea += (sv >> 3); + ctxt->dst.addr.mem.ea = address_mask(ctxt, + ctxt->dst.addr.mem.ea + (sv >> 3)); } /* only subword offset */ @@ -4638,7 +4638,8 @@ done_prefixes: rc = decode_operand(ctxt, &ctxt->dst, (ctxt->d >> DstShift) & OpMask); if (ctxt->rip_relative) - ctxt->memopp->addr.mem.ea += ctxt->_eip; + ctxt->memopp->addr.mem.ea = address_mask(ctxt, + ctxt->memopp->addr.mem.ea + ctxt->_eip); done: return (rc != X86EMUL_CONTINUE) ? EMULATION_FAILED : EMULATION_OK; |