From aaa8736370db1a78f0e8434344a484f9fd20be3b Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 27 Feb 2024 09:51:12 -0800 Subject: x86, relocs: Ignore relocations in .notes section 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 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 Signed-off-by: Kees Cook --- arch/x86/tools/relocs.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch') diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index a3bae2b24626..b029fb81ebee 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -653,6 +653,14 @@ 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++) { -- cgit v1.2.3-70-g09d2