From: Kees Cook keescook@chromium.org
[ Upstream commit aaa8736370db1a78f0e8434344a484f9fd20be3b ]
When building with CONFIG_XEN_PV=y, .text symbols are emitted into the .notes section so that Xen can find the "startup_xen" entry point. This information is used prior to booting the kernel, so relocations are not useful. In fact, performing relocations against the .notes section means that the KASLR base is exposed since /sys/kernel/notes is world-readable.
To avoid leaking the KASLR base without breaking unprivileged tools that are expecting to read /sys/kernel/notes, skip performing relocations in the .notes section. The values readable in .notes are then identical to those found in System.map.
Reported-by: Guixiong Wei guixiongwei@gmail.com Closes: https://lore.kernel.org/all/20240218073501.54555-1-guixiongwei@gmail.com/ Fixes: 5ead97c84fa7 ("xen: Core Xen implementation") Fixes: da1a679cde9b ("Add /sys/kernel/notes") Reviewed-by: Juergen Gross jgross@suse.com Signed-off-by: Kees Cook keescook@chromium.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/tools/relocs.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index 27c82207d3878..3167228ca1746 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -599,6 +599,14 @@ static void print_absolute_relocs(void) if (!(sec_applies->shdr.sh_flags & SHF_ALLOC)) { continue; } + /* + * Do not perform relocations in .notes section; any + * values there are meant for pre-boot consumption (e.g. + * startup_xen). + */ + if (sec_applies->shdr.sh_type == SHT_NOTE) { + continue; + } sh_symtab = sec_symtab->symtab; sym_strtab = sec_symtab->link->strtab; for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) {