Russell Currey <ruscur@xxxxxxxxxx> writes:
> On Tue, 2021-12-07 at 09:44 -0500, Joe Lawrence wrote:
>> On 11/23/21 3:15 AM, Russell Currey wrote:
>>
>> [[ cc += livepatching list ]]
>>
>> Hi Russell,
>>
>> Thanks for writing a minimal fix for stable / backporting. As I
>> mentioned on the github issue [1], this avoided the crashes I
>> reported
>> here and over on kpatch github [2]. I wasn't sure if this is the
>> final
>> version for stable, but feel free to add my:
>>
>> Tested-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
>
> Thanks Joe, as per the discussions on GitHub I think we're fine to use
> this patch for a fix for stable (unless there's new issues found or
> additional community feedback etc).
Hmm, I read the GitHub discussion as being that you were going to do
another version, which is why I haven't picked this up. But I guess you
and Christophe were talking about the non-minimal fix.
I know we want this to be minimal, but I think it should be checking
that patch_instruction() isn't failing.
Incremental diff to do that is below. It boots OK, are you able to throw
a livepatch test at it?
cheers
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index c25ef36c3ef4..5d77d3f5fbb5 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -429,8 +429,9 @@ static inline int create_stub(const Elf64_Shdr *sechdrs,
return create_ftrace_stub(entry, addr, me);
for (i = 0; i < sizeof(ppc64_stub_insns) / sizeof(u32); i++) {
- patch_instruction(&entry->jump[i],
- ppc_inst(ppc64_stub_insns[i]));
+ if (patch_instruction(&entry->jump[i],
+ ppc_inst(ppc64_stub_insns[i])))
+ return 0;
}
/* Stub uses address relative to r2. */
@@ -442,19 +443,24 @@ static inline int create_stub(const Elf64_Shdr *sechdrs,
}
pr_debug("Stub %p get data from reladdr %li\n", entry, reladdr);
- patch_instruction(&entry->jump[0],
- ppc_inst(entry->jump[0] | PPC_HA(reladdr)));
- patch_instruction(&entry->jump[1],
- ppc_inst(entry->jump[1] | PPC_LO(reladdr)));
+ if (patch_instruction(&entry->jump[0],
+ ppc_inst(entry->jump[0] | PPC_HA(reladdr))))
+ return 0;
+
+ if (patch_instruction(&entry->jump[1],
+ ppc_inst(entry->jump[1] | PPC_LO(reladdr))))
+ return 0;
// func_desc_t is 8 bytes if ABIv2, else 16 bytes
desc = func_desc(addr);
for (i = 0; i < sizeof(func_desc_t) / sizeof(u32); i++) {
- patch_instruction(((u32 *)&entry->funcdata) + i,
- ppc_inst(((u32 *)(&desc))[i]));
+ if (patch_instruction(((u32 *)&entry->funcdata) + i,
+ ppc_inst(((u32 *)(&desc))[i])))
+ return 0;
}
- patch_instruction(&entry->magic, ppc_inst(STUB_MAGIC));
+ if (patch_instruction(&entry->magic, ppc_inst(STUB_MAGIC)))
+ return 0;
return 1;
}
@@ -509,8 +515,11 @@ static int restore_r2(const char *name, u32 *instruction, struct module *me)
me->name, *instruction, instruction);
return 0;
}
+
/* ld r2,R2_STACK_OFFSET(r1) */
- patch_instruction(instruction, ppc_inst(PPC_INST_LD_TOC));
+ if (patch_instruction(instruction, ppc_inst(PPC_INST_LD_TOC)))
+ return 0;
+
return 1;
}
@@ -652,7 +661,10 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
/* Only replace bits 2 through 26 */
value = (*(uint32_t *)location & ~0x03fffffc)
| (value & 0x03fffffc);
- patch_instruction((u32 *)location, ppc_inst(value));
+
+ if (patch_instruction((u32 *)location, ppc_inst(value)))
+ return -EFAULT;
+
break;
case R_PPC64_REL64:
