From 050d18d1c65113b4558d86d53465ebe1d04910fb Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Mon, 30 Jan 2017 18:29:28 +0100 Subject: [PATCH] ARM: 8650/1: module: handle negative R_ARM_PREL31 addends correctly According to the spec 'ELF for the ARM Architecture' (IHI 0044E), addends for R_ARM_PREL31 relocations are 31-bit signed quantities, so we need to sign extend the value to 32 bits before it can be used as an offset in the calculation of the relocated value. We have not been bitten by this because these relocations are usually emitted against the start of a section, which means the addends never assume negative values in practice. But it is a bug nonetheless, so fix it. Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King --- arch/arm/kernel/module.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c index 4f14b5ce6535..80254b47dc34 100644 --- a/arch/arm/kernel/module.c +++ b/arch/arm/kernel/module.c @@ -155,8 +155,17 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, break; case R_ARM_PREL31: - offset = *(u32 *)loc + sym->st_value - loc; - *(u32 *)loc = offset & 0x7fffffff; + offset = (*(s32 *)loc << 1) >> 1; /* sign extend */ + offset += sym->st_value - loc; + if (offset >= 0x40000000 || offset < -0x40000000) { + pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n", + module->name, relindex, i, symname, + ELF32_R_TYPE(rel->r_info), loc, + sym->st_value); + return -ENOEXEC; + } + *(u32 *)loc &= 0x80000000; + *(u32 *)loc |= offset & 0x7fffffff; break; case R_ARM_MOVW_ABS_NC: -- 2.20.1