Commit 407a3c00ff ("compat/memory: fix build with old gcc") "fixed" a build issue by switching to the use of uninitialized data. Due to - the bounding of the uninitialized data item - the accessed area being outside of Xen space - arguments being properly verified by the native hypercall function this is not a security issue.
Reported-by: Marek Marczykowski-Górecki <marma...@invisiblethingslab.com> Signed-off-by: Jan Beulich <jbeul...@suse.com> --- a/xen/common/compat/memory.c +++ b/xen/common/compat/memory.c @@ -251,7 +251,7 @@ int compat_memory_op(unsigned int cmd, X unsigned int limit = (COMPAT_ARG_XLAT_SIZE - sizeof(*nat.atpb)) / (sizeof(nat.atpb->idxs.p) + sizeof(nat.atpb->gpfns.p)); /* Use an intermediate variable to suppress warnings on old gcc: */ - unsigned int size = cmp.atpb.size; + unsigned int size; xen_ulong_t *idxs = (void *)(nat.atpb + 1); xen_pfn_t *gpfns = (void *)(idxs + limit); /* @@ -262,8 +262,10 @@ int compat_memory_op(unsigned int cmd, X enum XLAT_add_to_physmap_batch_u u = XLAT_add_to_physmap_batch_u_res0; - if ( copy_from_guest(&cmp.atpb, compat, 1) || - !compat_handle_okay(cmp.atpb.idxs, size) || + if ( copy_from_guest(&cmp.atpb, compat, 1) ) + return -EFAULT; + size = cmp.atpb.size; + if ( !compat_handle_okay(cmp.atpb.idxs, size) || !compat_handle_okay(cmp.atpb.gpfns, size) || !compat_handle_okay(cmp.atpb.errs, size) ) return -EFAULT;
x86/32on64: properly honor add-to-physmap-batch's size Commit 407a3c00ff ("compat/memory: fix build with old gcc") "fixed" a build issue by switching to the use of uninitialized data. Due to - the bounding of the uninitialized data item - the accessed area being outside of Xen space - arguments being properly verified by the native hypercall function this is not a security issue. Reported-by: Marek Marczykowski-Górecki <marma...@invisiblethingslab.com> Signed-off-by: Jan Beulich <jbeul...@suse.com> --- a/xen/common/compat/memory.c +++ b/xen/common/compat/memory.c @@ -251,7 +251,7 @@ int compat_memory_op(unsigned int cmd, X unsigned int limit = (COMPAT_ARG_XLAT_SIZE - sizeof(*nat.atpb)) / (sizeof(nat.atpb->idxs.p) + sizeof(nat.atpb->gpfns.p)); /* Use an intermediate variable to suppress warnings on old gcc: */ - unsigned int size = cmp.atpb.size; + unsigned int size; xen_ulong_t *idxs = (void *)(nat.atpb + 1); xen_pfn_t *gpfns = (void *)(idxs + limit); /* @@ -262,8 +262,10 @@ int compat_memory_op(unsigned int cmd, X enum XLAT_add_to_physmap_batch_u u = XLAT_add_to_physmap_batch_u_res0; - if ( copy_from_guest(&cmp.atpb, compat, 1) || - !compat_handle_okay(cmp.atpb.idxs, size) || + if ( copy_from_guest(&cmp.atpb, compat, 1) ) + return -EFAULT; + size = cmp.atpb.size; + if ( !compat_handle_okay(cmp.atpb.idxs, size) || !compat_handle_okay(cmp.atpb.gpfns, size) || !compat_handle_okay(cmp.atpb.errs, size) ) return -EFAULT;
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