x86emul: also clip repetition count for STOS

Like MOVS, INS, and OUTS, STOS also has a special purpose hook, where
the hook function may legitimately have the same expectation as to the
request not straddling address space start/end.

Fixes: 5dfe4aa4eeb6 ("x86_emulate: Do not request emulation of REP instructions beyond the")
Reported-by: Fabian Specht <f.specht@tum.de>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: 8c5636b6c87777e6c2e4ffae28bffe1cfc189bfd
master date: 2025-04-22 11:24:20 +0200

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index 3d837f7e9efa4a333208d10faf1943e40baae54a..b1d192cbbf1e1326398c29688760016fa80f7269 100644 (file)
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2217,7 +2217,7 @@ x86_emulate(
 
         dst.bytes = src.bytes;
         dst.mem.seg = x86_seg_es;
-        dst.mem.off = truncate_ea(_regs.r(di));
+        dst.mem.off = truncate_ea_and_reps(_regs.r(di), nr_reps, dst.bytes);
         if ( (nr_reps == 1) || !ops->rep_stos ||
              ((rc = ops->rep_stos(&src.val,
                                   dst.mem.seg, dst.mem.off, dst.bytes,