From: Christophe Leroy <christophe.leroy@csgroup.eu> To: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Michael Ellerman <mpe@ellerman.id.au>, hch@lst.de, viro@zeniv.linux.org.uk, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org Subject: [PATCH v2] powerpc/mm: Fix KUAP warning by providing copy_from_kernel_nofault_allowed() Date: Mon, 7 Dec 2020 16:58:01 +0000 (UTC) [thread overview] Message-ID: <18bcb456d32a3e74f5ae241fd6f1580c092d07f5.1607360230.git.christophe.leroy@csgroup.eu> (raw) Since commit c33165253492 ("powerpc: use non-set_fs based maccess routines"), userspace access is not granted anymore when using copy_from_kernel_nofault() However, kthread_probe_data() uses copy_from_kernel_nofault() to check validity of pointers. When the pointer is NULL, it points to userspace, leading to a KUAP fault and triggering the following big hammer warning many times when you request a sysrq "show task": [ 1117.202054] ------------[ cut here ]------------ [ 1117.202102] Bug: fault blocked by AP register ! [ 1117.202261] WARNING: CPU: 0 PID: 377 at arch/powerpc/include/asm/nohash/32/kup-8xx.h:66 do_page_fault+0x4a8/0x5ec [ 1117.202310] Modules linked in: [ 1117.202428] CPU: 0 PID: 377 Comm: sh Tainted: G W 5.10.0-rc5-01340-g83f53be2de31-dirty #4175 [ 1117.202499] NIP: c0012048 LR: c0012048 CTR: 00000000 [ 1117.202573] REGS: cacdbb88 TRAP: 0700 Tainted: G W (5.10.0-rc5-01340-g83f53be2de31-dirty) [ 1117.202625] MSR: 00021032 <ME,IR,DR,RI> CR: 24082222 XER: 20000000 [ 1117.202899] [ 1117.202899] GPR00: c0012048 cacdbc40 c2929290 00000023 c092e554 00000001 c09865e8 c092e640 [ 1117.202899] GPR08: 00001032 00000000 00000000 00014efc 28082224 100d166a 100a0920 00000000 [ 1117.202899] GPR16: 100cac0c 100b0000 1080c3fc 1080d685 100d0000 100d0000 00000000 100a0900 [ 1117.202899] GPR24: 100d0000 c07892ec 00000000 c0921510 c21f4440 0000005c c0000000 cacdbc80 [ 1117.204362] NIP [c0012048] do_page_fault+0x4a8/0x5ec [ 1117.204461] LR [c0012048] do_page_fault+0x4a8/0x5ec [ 1117.204509] Call Trace: [ 1117.204609] [cacdbc40] [c0012048] do_page_fault+0x4a8/0x5ec (unreliable) [ 1117.204771] [cacdbc70] [c00112f0] handle_page_fault+0x8/0x34 [ 1117.204911] --- interrupt: 301 at copy_from_kernel_nofault+0x70/0x1c0 [ 1117.204979] NIP: c010dbec LR: c010dbac CTR: 00000001 [ 1117.205053] REGS: cacdbc80 TRAP: 0301 Tainted: G W (5.10.0-rc5-01340-g83f53be2de31-dirty) [ 1117.205104] MSR: 00009032 <EE,ME,IR,DR,RI> CR: 28082224 XER: 00000000 [ 1117.205416] DAR: 0000005c DSISR: c0000000 [ 1117.205416] GPR00: c0045948 cacdbd38 c2929290 00000001 00000017 00000017 00000027 0000000f [ 1117.205416] GPR08: c09926ec 00000000 00000000 3ffff000 24082224 [ 1117.206106] NIP [c010dbec] copy_from_kernel_nofault+0x70/0x1c0 [ 1117.206202] LR [c010dbac] copy_from_kernel_nofault+0x30/0x1c0 [ 1117.206258] --- interrupt: 301 [ 1117.206372] [cacdbd38] [c004bbb0] kthread_probe_data+0x44/0x70 (unreliable) [ 1117.206561] [cacdbd58] [c0045948] print_worker_info+0xe0/0x194 [ 1117.206717] [cacdbdb8] [c00548ac] sched_show_task+0x134/0x168 [ 1117.206851] [cacdbdd8] [c005a268] show_state_filter+0x70/0x100 [ 1117.206989] [cacdbe08] [c039baa0] sysrq_handle_showstate+0x14/0x24 [ 1117.207122] [cacdbe18] [c039bf18] __handle_sysrq+0xac/0x1d0 [ 1117.207257] [cacdbe48] [c039c0c0] write_sysrq_trigger+0x4c/0x74 [ 1117.207407] [cacdbe68] [c01fba48] proc_reg_write+0xb4/0x114 [ 1117.207550] [cacdbe88] [c0179968] vfs_write+0x12c/0x478 [ 1117.207686] [cacdbf08] [c0179e60] ksys_write+0x78/0x128 [ 1117.207826] [cacdbf38] [c00110d0] ret_from_syscall+0x0/0x34 [ 1117.207938] --- interrupt: c01 at 0xfd4e784 [ 1117.208008] NIP: 0fd4e784 LR: 0fe0f244 CTR: 10048d38 [ 1117.208083] REGS: cacdbf48 TRAP: 0c01 Tainted: G W (5.10.0-rc5-01340-g83f53be2de31-dirty) [ 1117.208134] MSR: 0000d032 <EE,PR,ME,IR,DR,RI> CR: 44002222 XER: 00000000 [ 1117.208470] [ 1117.208470] GPR00: 00000004 7fc34090 77bfb4e0 00000001 1080fa40 00000002 7400000f fefefeff [ 1117.208470] GPR08: 7f7f7f7f 10048d38 1080c414 7fc343c0 00000000 [ 1117.209104] NIP [0fd4e784] 0xfd4e784 [ 1117.209180] LR [0fe0f244] 0xfe0f244 [ 1117.209236] --- interrupt: c01 [ 1117.209274] Instruction dump: [ 1117.209353] 714a4000 418200f0 73ca0001 40820084 73ca0032 408200f8 73c90040 4082ff60 [ 1117.209727] 0fe00000 3c60c082 386399f4 48013b65 <0fe00000> 80010034 3860000b 7c0803a6 [ 1117.210102] ---[ end trace 1927c0323393af3e ]--- To avoid that, copy_from_kernel_nofault_allowed() is used to check whether the address is a valid kernel address. But the default version of it returns true for any address. Provide a powerpc version of copy_from_kernel_nofault_allowed() that returns false when the address is below TASK_USER_MAX, so that copy_from_kernel_nofault() will return -ERANGE. Reported-by: Qian Cai <qcai@redhat.com> Fixes: c33165253492 ("powerpc: use non-set_fs based maccess routines") Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- This issue was introduced in 5.10-rc1. I didn't mark it for stable, hopping it will go into 5.10 v2: Using is_kernel_addr() instead of comparison to TASK_SIZE_MAX. --- arch/powerpc/mm/Makefile | 2 +- arch/powerpc/mm/maccess.c | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) create mode 100644 arch/powerpc/mm/maccess.c diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile index 5e147986400d..55b4a8bd408a 100644 --- a/arch/powerpc/mm/Makefile +++ b/arch/powerpc/mm/Makefile @@ -5,7 +5,7 @@ ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC) -obj-y := fault.o mem.o pgtable.o mmap.o \ +obj-y := fault.o mem.o pgtable.o mmap.o maccess.o \ init_$(BITS).o pgtable_$(BITS).o \ pgtable-frag.o ioremap.o ioremap_$(BITS).o \ init-common.o mmu_context.o drmem.o diff --git a/arch/powerpc/mm/maccess.c b/arch/powerpc/mm/maccess.c new file mode 100644 index 000000000000..fa9a7a718fc6 --- /dev/null +++ b/arch/powerpc/mm/maccess.c @@ -0,0 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include <linux/uaccess.h> +#include <linux/kernel.h> + +bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) +{ + return is_kernel_addr((unsigned long)unsafe_src); +} -- 2.25.0
WARNING: multiple messages have this Message-ID (diff)
From: Christophe Leroy <christophe.leroy@csgroup.eu> To: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Michael Ellerman <mpe@ellerman.id.au>, hch@lst.de, viro@zeniv.linux.org.uk, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] powerpc/mm: Fix KUAP warning by providing copy_from_kernel_nofault_allowed() Date: Mon, 7 Dec 2020 16:58:01 +0000 (UTC) [thread overview] Message-ID: <18bcb456d32a3e74f5ae241fd6f1580c092d07f5.1607360230.git.christophe.leroy@csgroup.eu> (raw) Since commit c33165253492 ("powerpc: use non-set_fs based maccess routines"), userspace access is not granted anymore when using copy_from_kernel_nofault() However, kthread_probe_data() uses copy_from_kernel_nofault() to check validity of pointers. When the pointer is NULL, it points to userspace, leading to a KUAP fault and triggering the following big hammer warning many times when you request a sysrq "show task": [ 1117.202054] ------------[ cut here ]------------ [ 1117.202102] Bug: fault blocked by AP register ! [ 1117.202261] WARNING: CPU: 0 PID: 377 at arch/powerpc/include/asm/nohash/32/kup-8xx.h:66 do_page_fault+0x4a8/0x5ec [ 1117.202310] Modules linked in: [ 1117.202428] CPU: 0 PID: 377 Comm: sh Tainted: G W 5.10.0-rc5-01340-g83f53be2de31-dirty #4175 [ 1117.202499] NIP: c0012048 LR: c0012048 CTR: 00000000 [ 1117.202573] REGS: cacdbb88 TRAP: 0700 Tainted: G W (5.10.0-rc5-01340-g83f53be2de31-dirty) [ 1117.202625] MSR: 00021032 <ME,IR,DR,RI> CR: 24082222 XER: 20000000 [ 1117.202899] [ 1117.202899] GPR00: c0012048 cacdbc40 c2929290 00000023 c092e554 00000001 c09865e8 c092e640 [ 1117.202899] GPR08: 00001032 00000000 00000000 00014efc 28082224 100d166a 100a0920 00000000 [ 1117.202899] GPR16: 100cac0c 100b0000 1080c3fc 1080d685 100d0000 100d0000 00000000 100a0900 [ 1117.202899] GPR24: 100d0000 c07892ec 00000000 c0921510 c21f4440 0000005c c0000000 cacdbc80 [ 1117.204362] NIP [c0012048] do_page_fault+0x4a8/0x5ec [ 1117.204461] LR [c0012048] do_page_fault+0x4a8/0x5ec [ 1117.204509] Call Trace: [ 1117.204609] [cacdbc40] [c0012048] do_page_fault+0x4a8/0x5ec (unreliable) [ 1117.204771] [cacdbc70] [c00112f0] handle_page_fault+0x8/0x34 [ 1117.204911] --- interrupt: 301 at copy_from_kernel_nofault+0x70/0x1c0 [ 1117.204979] NIP: c010dbec LR: c010dbac CTR: 00000001 [ 1117.205053] REGS: cacdbc80 TRAP: 0301 Tainted: G W (5.10.0-rc5-01340-g83f53be2de31-dirty) [ 1117.205104] MSR: 00009032 <EE,ME,IR,DR,RI> CR: 28082224 XER: 00000000 [ 1117.205416] DAR: 0000005c DSISR: c0000000 [ 1117.205416] GPR00: c0045948 cacdbd38 c2929290 00000001 00000017 00000017 00000027 0000000f [ 1117.205416] GPR08: c09926ec 00000000 00000000 3ffff000 24082224 [ 1117.206106] NIP [c010dbec] copy_from_kernel_nofault+0x70/0x1c0 [ 1117.206202] LR [c010dbac] copy_from_kernel_nofault+0x30/0x1c0 [ 1117.206258] --- interrupt: 301 [ 1117.206372] [cacdbd38] [c004bbb0] kthread_probe_data+0x44/0x70 (unreliable) [ 1117.206561] [cacdbd58] [c0045948] print_worker_info+0xe0/0x194 [ 1117.206717] [cacdbdb8] [c00548ac] sched_show_task+0x134/0x168 [ 1117.206851] [cacdbdd8] [c005a268] show_state_filter+0x70/0x100 [ 1117.206989] [cacdbe08] [c039baa0] sysrq_handle_showstate+0x14/0x24 [ 1117.207122] [cacdbe18] [c039bf18] __handle_sysrq+0xac/0x1d0 [ 1117.207257] [cacdbe48] [c039c0c0] write_sysrq_trigger+0x4c/0x74 [ 1117.207407] [cacdbe68] [c01fba48] proc_reg_write+0xb4/0x114 [ 1117.207550] [cacdbe88] [c0179968] vfs_write+0x12c/0x478 [ 1117.207686] [cacdbf08] [c0179e60] ksys_write+0x78/0x128 [ 1117.207826] [cacdbf38] [c00110d0] ret_from_syscall+0x0/0x34 [ 1117.207938] --- interrupt: c01 at 0xfd4e784 [ 1117.208008] NIP: 0fd4e784 LR: 0fe0f244 CTR: 10048d38 [ 1117.208083] REGS: cacdbf48 TRAP: 0c01 Tainted: G W (5.10.0-rc5-01340-g83f53be2de31-dirty) [ 1117.208134] MSR: 0000d032 <EE,PR,ME,IR,DR,RI> CR: 44002222 XER: 00000000 [ 1117.208470] [ 1117.208470] GPR00: 00000004 7fc34090 77bfb4e0 00000001 1080fa40 00000002 7400000f fefefeff [ 1117.208470] GPR08: 7f7f7f7f 10048d38 1080c414 7fc343c0 00000000 [ 1117.209104] NIP [0fd4e784] 0xfd4e784 [ 1117.209180] LR [0fe0f244] 0xfe0f244 [ 1117.209236] --- interrupt: c01 [ 1117.209274] Instruction dump: [ 1117.209353] 714a4000 418200f0 73ca0001 40820084 73ca0032 408200f8 73c90040 4082ff60 [ 1117.209727] 0fe00000 3c60c082 386399f4 48013b65 <0fe00000> 80010034 3860000b 7c0803a6 [ 1117.210102] ---[ end trace 1927c0323393af3e ]--- To avoid that, copy_from_kernel_nofault_allowed() is used to check whether the address is a valid kernel address. But the default version of it returns true for any address. Provide a powerpc version of copy_from_kernel_nofault_allowed() that returns false when the address is below TASK_USER_MAX, so that copy_from_kernel_nofault() will return -ERANGE. Reported-by: Qian Cai <qcai@redhat.com> Fixes: c33165253492 ("powerpc: use non-set_fs based maccess routines") Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- This issue was introduced in 5.10-rc1. I didn't mark it for stable, hopping it will go into 5.10 v2: Using is_kernel_addr() instead of comparison to TASK_SIZE_MAX. --- arch/powerpc/mm/Makefile | 2 +- arch/powerpc/mm/maccess.c | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) create mode 100644 arch/powerpc/mm/maccess.c diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile index 5e147986400d..55b4a8bd408a 100644 --- a/arch/powerpc/mm/Makefile +++ b/arch/powerpc/mm/Makefile @@ -5,7 +5,7 @@ ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC) -obj-y := fault.o mem.o pgtable.o mmap.o \ +obj-y := fault.o mem.o pgtable.o mmap.o maccess.o \ init_$(BITS).o pgtable_$(BITS).o \ pgtable-frag.o ioremap.o ioremap_$(BITS).o \ init-common.o mmu_context.o drmem.o diff --git a/arch/powerpc/mm/maccess.c b/arch/powerpc/mm/maccess.c new file mode 100644 index 000000000000..fa9a7a718fc6 --- /dev/null +++ b/arch/powerpc/mm/maccess.c @@ -0,0 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include <linux/uaccess.h> +#include <linux/kernel.h> + +bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) +{ + return is_kernel_addr((unsigned long)unsafe_src); +} -- 2.25.0
next reply other threads:[~2020-12-07 16:59 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-07 16:58 Christophe Leroy [this message] 2020-12-07 16:58 ` [PATCH v2] powerpc/mm: Fix KUAP warning by providing copy_from_kernel_nofault_allowed() Christophe Leroy 2020-12-10 0:23 ` Michael Ellerman 2020-12-10 0:23 ` Michael Ellerman
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