From: Christophe Leroy christophe.leroy@csgroup.eu
commit 98694166c27d473c36b434bd3572934c2f2a16ab upstream.
An interrupt handler shall not be called from another interrupt handler otherwise this leads to problems like the following:
Kernel attempted to write user page (afd4fa84) - exploit attempt? (uid: 1000) ------------[ cut here ]------------ Bug: Write fault blocked by KUAP! WARNING: CPU: 0 PID: 1617 at arch/powerpc/mm/fault.c:230 do_page_fault+0x484/0x720 Modules linked in: CPU: 0 PID: 1617 Comm: sshd Tainted: G W 5.13.0-pmac-00010-g8393422eb77 #7 NIP: c001b77c LR: c001b77c CTR: 00000000 REGS: cb9e5bc0 TRAP: 0700 Tainted: G W (5.13.0-pmac-00010-g8393422eb77) MSR: 00021032 <ME,IR,DR,RI> CR: 24942424 XER: 00000000
GPR00: c001b77c cb9e5c80 c1582c00 00000021 3ffffbff 085b0000 00000027 c8eb644c GPR08: 00000023 00000000 00000000 00000000 24942424 0063f8c8 00000000 000186a0 GPR16: afd52dd4 afd52dd0 afd52dcc afd52dc8 0065a990 c07640c4 cb9e5e98 cb9e5e90 GPR24: 00000040 afd4fa96 00000040 02000000 c1fda6c0 afd4fa84 00000300 cb9e5cc0 NIP [c001b77c] do_page_fault+0x484/0x720 LR [c001b77c] do_page_fault+0x484/0x720 Call Trace: [cb9e5c80] [c001b77c] do_page_fault+0x484/0x720 (unreliable) [cb9e5cb0] [c000424c] DataAccess_virt+0xd4/0xe4 --- interrupt: 300 at __copy_tofrom_user+0x110/0x20c NIP: c001f9b4 LR: c03250a0 CTR: 00000004 REGS: cb9e5cc0 TRAP: 0300 Tainted: G W (5.13.0-pmac-00010-g8393422eb77) MSR: 00009032 <EE,ME,IR,DR,RI> CR: 48028468 XER: 20000000 DAR: afd4fa84 DSISR: 0a000000 GPR00: 20726f6f cb9e5d80 c1582c00 00000004 cb9e5e3a 00000016 afd4fa80 00000000 GPR08: 3835202d 72777872 2d78722d 00000004 28028464 0063f8c8 00000000 000186a0 GPR16: afd52dd4 afd52dd0 afd52dcc afd52dc8 0065a990 c07640c4 cb9e5e98 cb9e5e90 GPR24: 00000040 afd4fa96 00000040 cb9e5e0c 00000daa a0000000 cb9e5e98 afd4fa56 NIP [c001f9b4] __copy_tofrom_user+0x110/0x20c LR [c03250a0] _copy_to_iter+0x144/0x990 --- interrupt: 300 [cb9e5d80] [c03e89c0] n_tty_read+0xa4/0x598 (unreliable) [cb9e5df0] [c03e2a0c] tty_read+0xdc/0x2b4 [cb9e5e80] [c0156bf8] vfs_read+0x274/0x340 [cb9e5f00] [c01571ac] ksys_read+0x70/0x118 [cb9e5f30] [c0016048] ret_from_syscall+0x0/0x28 --- interrupt: c00 at 0xa7855c88 NIP: a7855c88 LR: a7855c5c CTR: 00000000 REGS: cb9e5f40 TRAP: 0c00 Tainted: G W (5.13.0-pmac-00010-g8393422eb77) MSR: 0000d032 <EE,PR,ME,IR,DR,RI> CR: 2402446c XER: 00000000
GPR00: 00000003 afd4ec70 a72137d0 0000000b afd4ecac 00004000 0065a990 00000800 GPR08: 00000000 a7947930 00000000 00000004 c15831b0 0063f8c8 00000000 000186a0 GPR16: afd52dd4 afd52dd0 afd52dcc afd52dc8 0065a990 0065a9e0 00000001 0065fac0 GPR24: 00000000 00000089 00664050 00000000 00668e30 a720c8dc a7943ff4 0065f9b0 NIP [a7855c88] 0xa7855c88 LR [a7855c5c] 0xa7855c5c --- interrupt: c00 Instruction dump: 3884aa88 38630178 48076861 807f0080 48042e45 2f830000 419e0148 3c80c079 3c60c076 38841be4 386301c0 4801f705 <0fe00000> 3860000b 4bfffe30 3c80c06b ---[ end trace fd69b91a8046c2e5 ]---
Here the problem is that by re-enterring an exception handler, kuap_save_and_lock() is called a second time with this time KUAP access locked, leading to regs->kuap being overwritten hence KUAP not being unlocked at exception exit as expected.
Do not call do_IRQ() from timer_interrupt() directly. Instead, redefine do_IRQ() as a standard function named __do_IRQ(), and call it from both do_IRQ() and time_interrupt() handlers.
Fixes: 3a96570ffceb ("powerpc: convert interrupt handlers to use wrappers") Cc: stable@vger.kernel.org # v5.12+ Reported-by: Stan Johnson userm57@yahoo.com Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Reviewed-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/c17d234f4927d39a1d7100864a8e1145323d33a0.162861192... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/include/asm/interrupt.h | 3 +++ arch/powerpc/include/asm/irq.h | 2 +- arch/powerpc/kernel/irq.c | 7 ++++++- arch/powerpc/kernel/time.c | 2 +- 4 files changed, 11 insertions(+), 3 deletions(-)
--- a/arch/powerpc/include/asm/interrupt.h +++ b/arch/powerpc/include/asm/interrupt.h @@ -531,6 +531,9 @@ DECLARE_INTERRUPT_HANDLER_NMI(hmi_except
DECLARE_INTERRUPT_HANDLER_ASYNC(TAUException);
+/* irq.c */ +DECLARE_INTERRUPT_HANDLER_ASYNC(do_IRQ); + void __noreturn unrecoverable_exception(struct pt_regs *regs);
void replay_system_reset(void); --- a/arch/powerpc/include/asm/irq.h +++ b/arch/powerpc/include/asm/irq.h @@ -53,7 +53,7 @@ extern void *mcheckirq_ctx[NR_CPUS]; extern void *hardirq_ctx[NR_CPUS]; extern void *softirq_ctx[NR_CPUS];
-extern void do_IRQ(struct pt_regs *regs); +void __do_IRQ(struct pt_regs *regs); extern void __init init_IRQ(void); extern void __do_irq(struct pt_regs *regs);
--- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -654,7 +654,7 @@ void __do_irq(struct pt_regs *regs) trace_irq_exit(regs); }
-DEFINE_INTERRUPT_HANDLER_ASYNC(do_IRQ) +void __do_IRQ(struct pt_regs *regs) { struct pt_regs *old_regs = set_irq_regs(regs); void *cursp, *irqsp, *sirqsp; @@ -678,6 +678,11 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(do_IRQ) set_irq_regs(old_regs); }
+DEFINE_INTERRUPT_HANDLER_ASYNC(do_IRQ) +{ + __do_IRQ(regs); +} + static void *__init alloc_vm_stack(void) { return __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, THREADINFO_GFP, --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -607,7 +607,7 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(timer_int
#if defined(CONFIG_PPC32) && defined(CONFIG_PPC_PMAC) if (atomic_read(&ppc_n_lost_interrupts) != 0) - do_IRQ(regs); + __do_IRQ(regs); #endif
old_regs = set_irq_regs(regs);