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Message-ID: <a0293b2d-7a43-49b7-8146-c20fd4be262f@westnet.com.au> Date: Tue, 13 Aug 2024 14:53:07 +1000 From: Greg Ungerer <gregungerer@...tnet.com.au> To: Max Filippov <jcmvbkbc@...il.com> Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, Eric Biederman <ebiederm@...ssion.com>, Kees Cook <keescook@...omium.org>, Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz> Subject: Re: [PATCH] binfmt_elf_fdpic: fix /proc/<pid>/auxv Hi Max, On 13/8/24 04:02, Max Filippov wrote: > Hi Greg, > > On Sun, Aug 11, 2024 at 7:26 PM Greg Ungerer <gregungerer@...tnet.com.au> wrote: >> On 23/3/24 05:54, Max Filippov wrote: >>> Althought FDPIC linux kernel provides /proc/<pid>/auxv files they are >>> empty because there's no code that initializes mm->saved_auxv in the >>> FDPIC ELF loader. >>> >>> Synchronize FDPIC ELF aux vector setup with ELF. Replace entry-by-entry >>> aux vector copying to userspace with initialization of mm->saved_auxv >>> first and then copying it to userspace as a whole. >>> >>> Signed-off-by: Max Filippov <jcmvbkbc@...il.com> >> >> This is breaking ARM nommu builds supporting fdpic and elf binaries for me. >> >> Tests I have for m68k and riscv nommu setups running elf binaries >> don't show any problems - I am only seeing this on ARM. >> >> >> ... >> Freeing unused kernel image (initmem) memory: 472K >> This architecture does not have kernel memory protection. >> Run /init as init process >> Internal error: Oops - undefined instruction: 0 [#1] ARM >> Modules linked in: >> CPU: 0 PID: 1 Comm: init Not tainted 6.10.0 #1 >> Hardware name: ARM-Versatile (Device Tree Support) >> PC is at load_elf_fdpic_binary+0xb34/0xb80 >> LR is at 0x0 >> pc : [<00109ce8>] lr : [<00000000>] psr: 80000153 >> sp : 00823e40 ip : 00000000 fp : 00b8fee4 >> r10: 009c9b80 r9 : 00b8ff80 r8 : 009ee800 >> r7 : 00000000 r6 : 009f7e80 r5 : 00b8fedc r4 : 00b87000 >> r3 : 00b8fed8 r2 : 00b8fee0 r1 : 00b87128 r0 : 00b8fef0 >> Flags: Nzcv IRQs on FIQs off Mode SVC_32 ISA ARM Segment none >> Control: 00091176 Table: 00000000 DAC: 00000000 >> Register r0 information: non-slab/vmalloc memory >> Register r1 information: slab/vmalloc mm_struct start 00b87000 pointer offset 296 size 428 >> Register r2 information: non-slab/vmalloc memory >> Register r3 information: non-slab/vmalloc memory >> Register r4 information: slab/vmalloc mm_struct start 00b87000 pointer offset 0 size 428 >> Register r5 information: non-slab/vmalloc memory >> Register r6 information: slab/vmalloc kmalloc-32 start 009f7e80 pointer offset 0 size 32 >> Register r7 information: non-slab/vmalloc memory >> Register r8 information: slab/vmalloc kmalloc-512 start 009ee800 pointer offset 0 size 512 >> Register r9 information: non-slab/vmalloc memory >> Register r10 information: slab/vmalloc kmalloc-128 start 009c9b80 pointer offset 0 size 128 >> Register r11 information: non-slab/vmalloc memory >> Register r12 information: non-slab/vmalloc memory >> Process init (pid: 1, stack limit = 0x(ptrval)) >> Stack: (0x00823e40 to 0x00824000) >> 3e40: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3e60: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3e80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3ea0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3ec0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3ee0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3f00: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3f20: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3f40: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3f60: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3f80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3fa0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3fe0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> Call trace: >> load_elf_fdpic_binary from bprm_execve+0x1b4/0x488 >> bprm_execve from kernel_execve+0x154/0x1e4 >> kernel_execve from kernel_init+0x4c/0x108 >> kernel_init from ret_from_fork+0x14/0x38 >> Exception stack(0x00823fb0 to 0x00823ff8) >> 3fa0: ???????? ???????? ???????? ???????? >> 3fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? >> 3fe0: ???????? ???????? ???????? ???????? ???????? ???????? >> Code: bad PC value >> ---[ end trace 0000000000000000 ]--- >> note: init[1] exited with irqs disabled >> Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b >> ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]--- >> >> >> The code around that PC is: >> >> 109cd0: e2833ff1 add r3, r3, #964 @ 0x3c4 >> 109cd4: e5933000 ldr r3, [r3] >> 109cd8: e5933328 ldr r3, [r3, #808] @ 0x328 >> 109cdc: e5933084 ldr r3, [r3, #132] @ 0x84 >> 109ce0: e5843034 str r3, [r4, #52] @ 0x34 >> 109ce4: eafffdbc b 1093dc <load_elf_fdpic_binary+0x228> >> 109ce8: e7f001f2 .word 0xe7f001f2 >> 109cec: eb09471d bl 35b968 <__stack_chk_fail> >> 109cf0: e59f0038 ldr r0, [pc, #56] @ 109d30 <load_elf_fdpic_binary+0xb7c> >> 109cf4: eb092f03 bl 355908 <_printk> >> 109cf8: eafffdb7 b 1093dc <load_elf_fdpic_binary+0x228> >> >> >> Reverting just this change gets it working again. >> >> Any idea what might be going on? > > Other than that the layout of the aux vector has slightly changed I don't > see anything. I can take a look at what's going on if you can share the > reproducer. I build the test binary using a simple script: https://github.com/gregungerer/simple-linux/blob/master/build-armnommu-linux-uclibc-fdpic.sh Run the resulting vmlinux and devicetree under qemu as per comments at top of that script. Note that that script has a revert of this change (at line 191), so you would need to take that out to reproduce the problem. This script will look for a couple of configs and a versatile patch: https://github.com/gregungerer/simple-linux/blob/master/configs/linux-6.10-armnommu-versatile.config https://github.com/gregungerer/simple-linux/blob/master/configs/uClibc-ng-1.0.49-armnommu-fdpic.config https://github.com/gregungerer/simple-linux/blob/master/configs/busybox-1.36.1.config https://github.com/gregungerer/simple-linux/blob/master/configs/rootfs.dev https://github.com/gregungerer/simple-linux/blob/master/patches/linux-6.10-armnommu-versatile.patch https://github.com/gregungerer/simple-linux/blob/master/patches/linux-6.10-binfmt_elf_fdpic-fix-proc-pid-auxv.patch Or you could just clone the whole small set in one step from: https://github.com/gregungerer/simple-linux.git If you need to me to run something I can do that easily too. Regards Greg
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