From 3b678768c0458e6d8d45fadf61423e44effed4cb Mon Sep 17 00:00:00 2001 From: Athira Rajeev Date: Fri, 29 Sep 2023 22:53:36 +0530 Subject: [PATCH 1/4] powerpc/pseries: Fix STK_PARAM access in the hcall tracing code In powerpc pseries system, below behaviour is observed while enabling tracing on hcall: # cd /sys/kernel/debug/tracing/ # cat events/powerpc/hcall_exit/enable 0 # echo 1 > events/powerpc/hcall_exit/enable # ls -bash: fork: Bad address Above is from power9 lpar with latest kernel. Past this, softlockup is observed. Initially while attempting via perf_event_open to use "PERF_TYPE_TRACEPOINT", kernel panic was observed. perf config used: ================ memset(&pe[1],0,sizeof(struct perf_event_attr)); pe[1].type=PERF_TYPE_TRACEPOINT; pe[1].size=96; pe[1].config=0x26ULL; /* 38 raw_syscalls/sys_exit */ pe[1].sample_type=0; /* 0 */ pe[1].read_format=PERF_FORMAT_TOTAL_TIME_ENABLED|PERF_FORMAT_TOTAL_TIME_RUNNING|PERF_FORMAT_ID|PERF_FORMAT_GROUP|0x10ULL; /* 1f */ pe[1].inherit=1; pe[1].precise_ip=0; /* arbitrary skid */ pe[1].wakeup_events=0; pe[1].bp_type=HW_BREAKPOINT_EMPTY; pe[1].config1=0x1ULL; Kernel panic logs: ================== Kernel attempted to read user page (8) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x00000008 Faulting instruction address: 0xc0000000004c2814 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: nfnetlink bonding tls rfkill sunrpc dm_service_time dm_multipath pseries_rng xts vmx_crypto xfs libcrc32c sd_mod t10_pi crc64_rocksoft crc64 sg ibmvfc scsi_transport_fc ibmveth dm_mirror dm_region_hash dm_log dm_mod fuse CPU: 0 PID: 1431 Comm: login Not tainted 6.4.0+ #1 Hardware name: IBM,8375-42A POWER9 (raw) 0x4e0202 0xf000005 of:IBM,FW950.30 (VL950_892) hv:phyp pSeries NIP page_remove_rmap+0x44/0x320 LR wp_page_copy+0x384/0xec0 Call Trace: 0xc00000001416e400 (unreliable) wp_page_copy+0x384/0xec0 __handle_mm_fault+0x9d4/0xfb0 handle_mm_fault+0xf0/0x350 ___do_page_fault+0x48c/0xc90 hash__do_page_fault+0x30/0x70 do_hash_fault+0x1a4/0x330 data_access_common_virt+0x198/0x1f0 --- interrupt: 300 at 0x7fffae971abc git bisect tracked this down to below commit: 'commit baa49d81a94b ("powerpc/pseries: hvcall stack frame overhead")' This commit changed STACK_FRAME_OVERHEAD (112 ) to STACK_FRAME_MIN_SIZE (32 ) since 32 bytes is the minimum size for ELFv2 stack. With the latest kernel, when running on ELFv2, STACK_FRAME_MIN_SIZE is used to allocate stack size. During plpar_hcall_trace, first call is made to HCALL_INST_PRECALL which saves the registers and allocates new stack frame. In the plpar_hcall_trace code, STK_PARAM is accessed at two places. 1. To save r4: std r4,STK_PARAM(R4)(r1) 2. To access r4 back: ld r12,STK_PARAM(R4)(r1) HCALL_INST_PRECALL precall allocates a new stack frame. So all the stack parameter access after the precall, needs to be accessed with +STACK_FRAME_MIN_SIZE. So the store instruction should be: std r4,STACK_FRAME_MIN_SIZE+STK_PARAM(R4)(r1) If the "std" is not updated with STACK_FRAME_MIN_SIZE, we will end up with overwriting stack contents and cause corruption. But instead of updating 'std', we can instead remove it since HCALL_INST_PRECALL already saves it to the correct location. similarly load instruction should be: ld r12,STACK_FRAME_MIN_SIZE+STK_PARAM(R4)(r1) Fix the load instruction to correctly access the stack parameter with +STACK_FRAME_MIN_SIZE and remove the store of r4 since the precall saves it correctly. Cc: stable@vger.kernel.org # v6.2+ Fixes: baa49d81a94b ("powerpc/pseries: hvcall stack frame overhead") Co-developed-by: Naveen N Rao Signed-off-by: Naveen N Rao Signed-off-by: Athira Rajeev Signed-off-by: Michael Ellerman Link: https://msgid.link/20230929172337.7906-1-atrajeev@linux.vnet.ibm.com --- arch/powerpc/platforms/pseries/hvCall.S | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S index bae45b358a094..2addf2ea03f09 100644 --- a/arch/powerpc/platforms/pseries/hvCall.S +++ b/arch/powerpc/platforms/pseries/hvCall.S @@ -184,7 +184,6 @@ _GLOBAL_TOC(plpar_hcall) plpar_hcall_trace: HCALL_INST_PRECALL(R5) - std r4,STK_PARAM(R4)(r1) mr r0,r4 mr r4,r5 @@ -196,7 +195,7 @@ plpar_hcall_trace: HVSC - ld r12,STK_PARAM(R4)(r1) + ld r12,STACK_FRAME_MIN_SIZE+STK_PARAM(R4)(r1) std r4,0(r12) std r5,8(r12) std r6,16(r12) @@ -296,7 +295,6 @@ _GLOBAL_TOC(plpar_hcall9) plpar_hcall9_trace: HCALL_INST_PRECALL(R5) - std r4,STK_PARAM(R4)(r1) mr r0,r4 mr r4,r5 From dfb5f8cbd5992d5769edfd3e059fad9e0b8bdafb Mon Sep 17 00:00:00 2001 From: Athira Rajeev Date: Fri, 29 Sep 2023 22:53:37 +0530 Subject: [PATCH 2/4] powerpc/pseries: Remove unused r0 in the hcall tracing code In the plpar_hcall trace code, currently we use r0 to store the value of r4. But this value is not used subsequently in the code. Hence remove this unused save to r0 in plpar_hcall and plpar_hcall9 Suggested-by: Naveen N Rao Signed-off-by: Athira Rajeev Signed-off-by: Michael Ellerman Link: https://msgid.link/20230929172337.7906-2-atrajeev@linux.vnet.ibm.com --- arch/powerpc/platforms/pseries/hvCall.S | 4 ---- 1 file changed, 4 deletions(-) diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S index 2addf2ea03f09..2b0cac6fb61f8 100644 --- a/arch/powerpc/platforms/pseries/hvCall.S +++ b/arch/powerpc/platforms/pseries/hvCall.S @@ -184,8 +184,6 @@ _GLOBAL_TOC(plpar_hcall) plpar_hcall_trace: HCALL_INST_PRECALL(R5) - mr r0,r4 - mr r4,r5 mr r5,r6 mr r6,r7 @@ -295,8 +293,6 @@ _GLOBAL_TOC(plpar_hcall9) plpar_hcall9_trace: HCALL_INST_PRECALL(R5) - mr r0,r4 - mr r4,r5 mr r5,r6 mr r6,r7 From 5d9cea8a552ee122e21fbd5a3c5d4eb85f648e06 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Mon, 25 Sep 2023 20:31:15 +0200 Subject: [PATCH 3/4] powerpc/8xx: Fix pte_access_permitted() for PAGE_NONE On 8xx, PAGE_NONE is handled by setting _PAGE_NA instead of clearing _PAGE_USER. But then pte_user() returns 1 also for PAGE_NONE. As _PAGE_NA prevent reads, add a specific version of pte_read() that returns 0 when _PAGE_NA is set instead of always returning 1. Fixes: 351750331fc1 ("powerpc/mm: Introduce _PAGE_NA") Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/57bcfbe578e43123f9ed73e040229b80f1ad56ec.1695659959.git.christophe.leroy@csgroup.eu --- arch/powerpc/include/asm/nohash/32/pte-8xx.h | 7 +++++++ arch/powerpc/include/asm/nohash/pgtable.h | 2 ++ 2 files changed, 9 insertions(+) diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h index 21f681ee535a2..e6fe1d5731f2c 100644 --- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h +++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h @@ -94,6 +94,13 @@ static inline pte_t pte_wrprotect(pte_t pte) #define pte_wrprotect pte_wrprotect +static inline int pte_read(pte_t pte) +{ + return (pte_val(pte) & _PAGE_RO) != _PAGE_NA; +} + +#define pte_read pte_read + static inline int pte_write(pte_t pte) { return !(pte_val(pte) & _PAGE_RO); diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h index 56ea48276356c..c721478c59347 100644 --- a/arch/powerpc/include/asm/nohash/pgtable.h +++ b/arch/powerpc/include/asm/nohash/pgtable.h @@ -25,7 +25,9 @@ static inline int pte_write(pte_t pte) return pte_val(pte) & _PAGE_RW; } #endif +#ifndef pte_read static inline int pte_read(pte_t pte) { return 1; } +#endif static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY; } static inline int pte_special(pte_t pte) { return pte_val(pte) & _PAGE_SPECIAL; } static inline int pte_none(pte_t pte) { return (pte_val(pte) & ~_PTE_NONE_MASK) == 0; } From 5ea0bbaa32e8f54e9a57cfee4a3b8769b80be0d2 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Mon, 25 Sep 2023 20:31:16 +0200 Subject: [PATCH 4/4] powerpc/64e: Fix wrong test in __ptep_test_and_clear_young() Commit 45201c879469 ("powerpc/nohash: Remove hash related code from nohash headers.") replaced: if ((pte_val(*ptep) & (_PAGE_ACCESSED | _PAGE_HASHPTE)) == 0) return 0; By: if (pte_young(*ptep)) return 0; But it should be: if (!pte_young(*ptep)) return 0; Fix it. Fixes: 45201c879469 ("powerpc/nohash: Remove hash related code from nohash headers.") Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/8bb7f06494e21adada724ede47a4c3d97e879d40.1695659959.git.christophe.leroy@csgroup.eu --- arch/powerpc/include/asm/nohash/64/pgtable.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h index 5cd9acf58a7db..eb6891e34cbde 100644 --- a/arch/powerpc/include/asm/nohash/64/pgtable.h +++ b/arch/powerpc/include/asm/nohash/64/pgtable.h @@ -197,7 +197,7 @@ static inline int __ptep_test_and_clear_young(struct mm_struct *mm, { unsigned long old; - if (pte_young(*ptep)) + if (!pte_young(*ptep)) return 0; old = pte_update(mm, addr, ptep, _PAGE_ACCESSED, 0, 0); return (old & _PAGE_ACCESSED) != 0;