On Wed, 31 Mar 2021 14:07:04 +0000 (UTC), Christophe Leroy wrote:
> PPC32 encounters a KUAP fault when trying to handle a signal with
> VDSO unmapped.
>
> Kernel attempted to read user page (7fc07ec0) - exploit attempt? (uid:
> 0)
> BUG: Unable to handle kernel data access on read at 0x7fc07ec0
> Faulting instruction address: 0xc00111d4
> Oops: Kernel access of bad area, sig: 11 [#1]
> BE PAGE_SIZE=16K PREEMPT CMPC885
> CPU: 0 PID: 353 Comm: sigreturn_vdso Not tainted
> 5.12.0-rc4-s3k-dev-01553-gb30c310ea220 #4814
> NIP: c00111d4 LR: c0005a28 CTR: 00000000
> REGS: cadb3dd0 TRAP: 0300 Not tainted
> (5.12.0-rc4-s3k-dev-01553-gb30c310ea220)
> MSR: 00009032 <EE,ME,IR,DR,RI> CR: 48000884 XER: 20000000
> DAR: 7fc07ec0 DSISR: 88000000
> GPR00: c0007788 cadb3e90 c28d4a40 7fc07ec0 7fc07ed0 000004e0 7fc07ce0
> 00000000
> GPR08: 00000001 00000001 7fc07ec0 00000000 28000282 1001b828 100a0920
> 00000000
> GPR16: 100cac0c 100b0000 105c43a4 105c5685 100d0000 100d0000 100d0000
> 100b2e9e
> GPR24: ffffffff 105c43c8 00000000 7fc07ec8 cadb3f40 cadb3ec8 c28d4a40
> 00000000
> NIP [c00111d4] flush_icache_range+0x90/0xb4
> LR [c0005a28] handle_signal32+0x1bc/0x1c4
> Call Trace:
> [cadb3e90] [100d0000] 0x100d0000 (unreliable)
> [cadb3ec0] [c0007788] do_notify_resume+0x260/0x314
> [cadb3f20] [c000c764] syscall_exit_prepare+0x120/0x184
> [cadb3f30] [c00100b4] ret_from_syscall+0xc/0x28
> --- interrupt: c00 at 0xfe807f8
> NIP: 0fe807f8 LR: 10001060 CTR: c0139378
> REGS: cadb3f40 TRAP: 0c00 Not tainted
> (5.12.0-rc4-s3k-dev-01553-gb30c310ea220)
> MSR: 0000d032 <EE,PR,ME,IR,DR,RI> CR: 28000482 XER: 20000000
>
> [...]
Applied to powerpc/fixes.
[1/1] powerpc/signal32: Fix Oops on sigreturn with unmapped VDSO
https://git.kernel.org/powerpc/c/acca57217c688c5bbbd5140974533d81e8757cc9
cheers
