Re: [PATCH 1/5] MIPS: Bail on unsupported module relocs

James Hogan
2016-02-03T12:23:35Z

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On Wed, Feb 03, 2016 at 03:44:41AM +0000, Paul Burton wrote:
> When an unsupported reloc is encountered in a module, we currently
> blindly branch to whatever would be at its entry in the reloc handler
> function pointer arrays. This may be NULL, or if the unsupported reloc
> has a type greater than that of the supported reloc with the highest
> type then we'll dereference some value after the function pointer array
> & branch to that. The result is at best a kernel oops.
>
> Fix this by checking that the reloc type has an entry in the function
> pointer array (ie. is less than the number of items in the array) and
> that the handler is non-NULL, returning an error code to fail the module
> load if no handler is found.
>
> Signed-off-by: Paul Burton <paul.burton@imgtec.com>
> Cc: James Hogan <james.hogan@imgtec.com>

Reviewed-by: James Hogan <james.hogan@imgtec.com>

Cheers
James

> ---
>
> arch/mips/kernel/module-rela.c | 19 ++++++++++++++++---
> arch/mips/kernel/module.c | 19 ++++++++++++++++---
> 2 files changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/arch/mips/kernel/module-rela.c b/arch/mips/kernel/module-rela.c
> index 2b70723..769e316 100644
> --- a/arch/mips/kernel/module-rela.c
> +++ b/arch/mips/kernel/module-rela.c
> @@ -109,9 +109,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> struct module *me)
> {
> Elf_Mips_Rela *rel = (void *) sechdrs[relsec].sh_addr;
> + int (*handler)(struct module *me, u32 *location, Elf_Addr v);
> Elf_Sym *sym;
> u32 *location;
> - unsigned int i;
> + unsigned int i, type;
> Elf_Addr v;
> int res;
>
> @@ -134,9 +135,21 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> return -ENOENT;
> }
>
> - v = sym->st_value + rel[i].r_addend;
> + type = ELF_MIPS_R_TYPE(rel[i]);
> +
> + if (type < ARRAY_SIZE(reloc_handlers_rela))
> + handler = reloc_handlers_rela[type];
> + else
> + handler = NULL;
>
> - res = reloc_handlers_rela[ELF_MIPS_R_TYPE(rel[i])](me, location, v);
> + if (!handler) {
> + pr_warn("%s: Unknown relocation type %u\n",
> + me->name, type);
> + return -EINVAL;
> + }
> +
> + v = sym->st_value + rel[i].r_addend;
> + res = handler(me, location, v);
> if (res)
> return res;
> }
> diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
> index 1833f51..2adf572 100644
> --- a/arch/mips/kernel/module.c
> +++ b/arch/mips/kernel/module.c
> @@ -197,9 +197,10 @@ int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
> struct module *me)
> {
> Elf_Mips_Rel *rel = (void *) sechdrs[relsec].sh_addr;
> + int (*handler)(struct module *me, u32 *location, Elf_Addr v);
> Elf_Sym *sym;
> u32 *location;
> - unsigned int i;
> + unsigned int i, type;
> Elf_Addr v;
> int res;
>
> @@ -223,9 +224,21 @@ int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
> return -ENOENT;
> }
>
> - v = sym->st_value;
> + type = ELF_MIPS_R_TYPE(rel[i]);
> +
> + if (type < ARRAY_SIZE(reloc_handlers_rel))
> + handler = reloc_handlers_rel[type];
> + else
> + handler = NULL;
>
> - res = reloc_handlers_rel[ELF_MIPS_R_TYPE(rel[i])](me, location, v);
> + if (!handler) {
> + pr_warn("%s: Unknown relocation type %u\n",
> + me->name, type);
> + return -EINVAL;
> + }
> +
> + v = sym->st_value;
> + res = handler(me, location, v);
> if (res)
> return res;
> }
> --
> 2.7.0
>

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