This is a note to let you know that I've just added the patch titled
x86/module: Detect and skip invalid relocations
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: x86-module-detect-and-skip-invalid-relocations.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From eda9cec4c9a12208a6f69fbe68f72a6311d50032 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf jpoimboe@redhat.com Date: Fri, 3 Nov 2017 07:58:54 -0500 Subject: x86/module: Detect and skip invalid relocations
From: Josh Poimboeuf jpoimboe@redhat.com
commit eda9cec4c9a12208a6f69fbe68f72a6311d50032 upstream.
There have been some cases where external tooling (e.g., kpatch-build) creates a corrupt relocation which targets the wrong address. This is a silent failure which can corrupt memory in unexpected places.
On x86, the bytes of data being overwritten by relocations are always initialized to zero beforehand. Use that knowledge to add sanity checks to detect such cases before they corrupt memory.
Signed-off-by: Josh Poimboeuf jpoimboe@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: jeyu@kernel.org Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/37450d6c6225e54db107fba447ce9e56e5f758e9.1509713553... [ Restructured the messages, as it's unclear whether the relocation or the target is corrupted. ] Signed-off-by: Ingo Molnar mingo@kernel.org Cc: Matthias Kaehlcke mka@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kernel/module.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
--- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -170,19 +170,27 @@ int apply_relocate_add(Elf64_Shdr *sechd case R_X86_64_NONE: break; case R_X86_64_64: + if (*(u64 *)loc != 0) + goto invalid_relocation; *(u64 *)loc = val; break; case R_X86_64_32: + if (*(u32 *)loc != 0) + goto invalid_relocation; *(u32 *)loc = val; if (val != *(u32 *)loc) goto overflow; break; case R_X86_64_32S: + if (*(s32 *)loc != 0) + goto invalid_relocation; *(s32 *)loc = val; if ((s64)val != *(s32 *)loc) goto overflow; break; case R_X86_64_PC32: + if (*(u32 *)loc != 0) + goto invalid_relocation; val -= (u64)loc; *(u32 *)loc = val; #if 0 @@ -198,6 +206,11 @@ int apply_relocate_add(Elf64_Shdr *sechd } return 0;
+invalid_relocation: + pr_err("x86/modules: Skipping invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n", + (int)ELF64_R_TYPE(rel[i].r_info), loc, val); + return -ENOEXEC; + overflow: pr_err("overflow in relocation type %d val %Lx\n", (int)ELF64_R_TYPE(rel[i].r_info), val);
Patches currently in stable-queue which might be from jpoimboe@redhat.com are
queue-4.4/x86-module-detect-and-skip-invalid-relocations.patch queue-4.4/nospec-include-asm-barrier.h-dependency.patch