On 19/04/2024 11:02 am, Roger Pau Monne wrote: > Livepatch payloads containing symbols that belong to init sections can only > lead to page faults later on, as by the time the livepatch is loaded init > sections have already been freed. > > Refuse to resolve such symbols and return an error instead. > > Note such resolutions are only relevant for symbols that point to undefined > sections (SHN_UNDEF), as that implies the symbol is not in the current payload > and hence must either be a Xen or a different livepatch payload symbol. > > Do not allow to resolve symbols that point to __init_begin, as that address is > also unmapped. On the other hand, __init_end is not unmapped, and hence allow > resolutions against it. > > Signed-off-by: Roger Pau Monné <roger....@citrix.com>
Reviewed-by: Andrew Cooper <andrew.coop...@citrix.com>, although ... > --- > Changes since v1: > - Fix off-by-one in range checking. > --- > xen/common/livepatch_elf.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/xen/common/livepatch_elf.c b/xen/common/livepatch_elf.c > index 45d73912a3cd..a67101eadc02 100644 > --- a/xen/common/livepatch_elf.c > +++ b/xen/common/livepatch_elf.c > @@ -4,6 +4,7 @@ > > #include <xen/errno.h> > #include <xen/lib.h> > +#include <xen/sections.h> > #include <xen/symbols.h> > #include <xen/livepatch_elf.h> > #include <xen/livepatch.h> > @@ -310,6 +311,21 @@ int livepatch_elf_resolve_symbols(struct livepatch_elf > *elf) > break; > } > } > + > + /* > + * Ensure not an init symbol. Only applicable to Xen symbols, as > + * livepatch payloads don't have init sections or equivalent. > + */ > + else if ( st_value >= (uintptr_t)&__init_begin && > + st_value < (uintptr_t)&__init_end ) ... I normally vertically the (casts) in cases like this for improved legibility. Happy to fold on commit. ~Andrew
