From: Joe Lawrence <joe.lawrence@redhat.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Miroslav Benes <mbenes@suse.cz>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Jessica Yu <jeyu@kernel.org>,
linux-s390@vger.kernel.org, heiko.carstens@de.ibm.com,
Vasily Gorbik <gor@linux.ibm.com>
Subject: Re: [PATCH v2 6/9] s390/module: Use s390_kernel_write() for late relocations
Date: Thu, 23 Apr 2020 22:35:21 -0400 [thread overview]
Message-ID: <20200424023521.GA22117@redhat.com> (raw)
In-Reply-To: <20200423232657.7minzcsysnhp474w@treble>
On Thu, Apr 23, 2020 at 06:26:57PM -0500, Josh Poimboeuf wrote:
> On Thu, Apr 23, 2020 at 01:10:30PM -0500, Josh Poimboeuf wrote:
> > Mystery solved:
> >
> > $ CROSS_COMPILE=s390x-linux-gnu- scripts/faddr2line vmlinux apply_rela+0x16a/0x520
> > apply_rela+0x16a/0x520:
> > apply_rela at arch/s390/kernel/module.c:336
> >
> > which corresponds to the following code in apply_rela():
> >
> >
> > case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */
> > if (info->plt_initialized == 0) {
> > unsigned int *ip;
> > ip = me->core_layout.base + me->arch.plt_offset +
> > info->plt_offset;
> > ip[0] = 0x0d10e310; /* basr 1,0 */
> > ip[1] = 0x100a0004; /* lg 1,10(1) */
> >
> >
> > Notice how it's writing directly to text... oops.
>
> Here's a fix, using write() for the PLT and the GOT.
>
> diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
> index 2798329ebb74..fe446f42818f 100644
> --- a/arch/s390/kernel/module.c
> +++ b/arch/s390/kernel/module.c
> @@ -297,7 +297,7 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
>
> gotent = me->core_layout.base + me->arch.got_offset +
> info->got_offset;
> - *gotent = val;
> + write(gotent, &val, sizeof(*gotent));
> info->got_initialized = 1;
> }
> val = info->got_offset + rela->r_addend;
> @@ -330,25 +330,29 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
> case R_390_PLTOFF32: /* 32 bit offset from GOT to PLT. */
> case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */
> if (info->plt_initialized == 0) {
> - unsigned int *ip;
> + unsigned int *ip, insn[5];
> +
> ip = me->core_layout.base + me->arch.plt_offset +
> info->plt_offset;
Would it be too paranoid to declare:
const unsigned int *ip = me->core_layout.base +
me->arch.plt_offset +
info->plt_offset;
That would trip an assignment to read-only error if someone were tempted
to write directly through the pointer in the future. Ditto for Elf_Addr
*gotent pointer in the R_390_GOTPLTENT case.
-- Joe
next prev parent reply other threads:[~2020-04-24 2:35 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-17 14:04 [PATCH v2 0/9] livepatch,module: Remove .klp.arch and module_disable_ro() Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 1/9] livepatch: Disallow vmlinux.ko Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 2/9] livepatch: Apply vmlinux-specific KLP relocations early Josh Poimboeuf
2020-04-20 17:57 ` Joe Lawrence
2020-04-20 18:25 ` Josh Poimboeuf
2020-04-20 19:01 ` Joe Lawrence
2020-04-20 19:11 ` Josh Poimboeuf
2020-04-20 19:49 ` Joe Lawrence
2020-04-20 19:51 ` Josh Poimboeuf
2020-04-23 1:10 ` Joe Lawrence
2020-04-21 11:54 ` Miroslav Benes
2020-04-17 14:04 ` [PATCH v2 3/9] livepatch: Remove .klp.arch Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 4/9] livepatch: Prevent module-specific KLP rela sections from referencing vmlinux symbols Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 5/9] s390: Change s390_kernel_write() return type to match memcpy() Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 6/9] s390/module: Use s390_kernel_write() for late relocations Josh Poimboeuf
2020-04-22 12:28 ` Miroslav Benes
2020-04-24 13:43 ` Josh Poimboeuf
2020-04-22 14:40 ` Gerald Schaefer
2020-04-22 15:21 ` Gerald Schaefer
2020-04-22 19:46 ` Josh Poimboeuf
2020-04-23 12:33 ` Gerald Schaefer
2020-04-23 13:22 ` Miroslav Benes
2020-04-23 14:12 ` Josh Poimboeuf
2020-04-23 18:10 ` Josh Poimboeuf
2020-04-23 23:26 ` Josh Poimboeuf
2020-04-24 2:35 ` Joe Lawrence [this message]
2020-04-24 4:12 ` Josh Poimboeuf
2020-04-24 7:20 ` Christian Borntraeger
2020-04-24 13:37 ` Josh Poimboeuf
2020-04-30 14:38 ` Joe Lawrence
2020-04-30 16:48 ` Josh Poimboeuf
2020-04-30 17:04 ` Joe Lawrence
2020-04-23 14:21 ` Joe Lawrence
2020-04-17 14:04 ` [PATCH v2 7/9] x86/module: Use text_poke() " Josh Poimboeuf
2020-04-17 14:29 ` Peter Zijlstra
2020-04-17 14:51 ` Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 8/9] livepatch: Remove module_disable_ro() usage Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 9/9] module: Remove module_disable_ro() Josh Poimboeuf
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