diff options
author | Richard Weinberger <richard@nod.at> | 2013-08-17 20:46:00 +0400 |
---|---|---|
committer | Richard Weinberger <richard@nod.at> | 2013-09-07 12:38:34 +0400 |
commit | f75b1b1bedfb498cc43a992ce4d7ed8df3b1e770 (patch) | |
tree | e7afc9647b9cc80fb95ee9dae7d9532b67efdc01 /arch/um | |
parent | 65984ff9d2179a97e5a11aaef1e86fdb276cfad5 (diff) | |
download | linux-f75b1b1bedfb498cc43a992ce4d7ed8df3b1e770.tar.xz |
um: Implement probe_kernel_read()
UML needs it's own probe_kernel_read() to handle kernel
mode faults correctly.
The implementation uses mincore() on the host side to detect
whether a page is owned by the UML kernel process.
This fixes also a possible crash when sysrq-t is used.
Starting with 3.10 sysrq-t calls probe_kernel_read() to
read details from the kernel workers. As kernel worker are
completely async pointers may turn NULL while reading them.
Cc: <stian@nixia.no>
Cc: <tj@kernel.org>
Cc: <stable@vger.kernel.org> # 3.10.x
Signed-off-by: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'arch/um')
-rw-r--r-- | arch/um/include/shared/os.h | 1 | ||||
-rw-r--r-- | arch/um/kernel/Makefile | 2 | ||||
-rw-r--r-- | arch/um/kernel/maccess.c | 24 | ||||
-rw-r--r-- | arch/um/os-Linux/process.c | 52 |
4 files changed, 78 insertions, 1 deletions
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h index 95feaa47a2fb..c70a234a3f8c 100644 --- a/arch/um/include/shared/os.h +++ b/arch/um/include/shared/os.h @@ -200,6 +200,7 @@ extern int os_unmap_memory(void *addr, int len); extern int os_drop_memory(void *addr, int length); extern int can_drop_memory(void); extern void os_flush_stdout(void); +extern int os_mincore(void *addr, unsigned long len); /* execvp.c */ extern int execvp_noalloc(char *buf, const char *file, char *const argv[]); diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile index babe21826e3e..d8b78a03855c 100644 --- a/arch/um/kernel/Makefile +++ b/arch/um/kernel/Makefile @@ -13,7 +13,7 @@ clean-files := obj-y = config.o exec.o exitcode.o irq.o ksyms.o mem.o \ physmem.o process.o ptrace.o reboot.o sigio.o \ signal.o smp.o syscall.o sysrq.o time.o tlb.o trap.o \ - um_arch.o umid.o skas/ + um_arch.o umid.o maccess.o skas/ obj-$(CONFIG_BLK_DEV_INITRD) += initrd.o obj-$(CONFIG_GPROF) += gprof_syms.o diff --git a/arch/um/kernel/maccess.c b/arch/um/kernel/maccess.c new file mode 100644 index 000000000000..1f3d5c4910d1 --- /dev/null +++ b/arch/um/kernel/maccess.c @@ -0,0 +1,24 @@ +/* + * Copyright (C) 2013 Richard Weinberger <richrd@nod.at> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/uaccess.h> +#include <linux/kernel.h> +#include <os.h> + +long probe_kernel_read(void *dst, const void *src, size_t size) +{ + void *psrc = (void *)rounddown((unsigned long)src, PAGE_SIZE); + + if ((unsigned long)src < PAGE_SIZE || size <= 0) + return -EFAULT; + + if (os_mincore(psrc, size + src - psrc) <= 0) + return -EFAULT; + + return __probe_kernel_read(dst, src, size); +} diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c index b8f34c9e53ae..67b9c8f5a89e 100644 --- a/arch/um/os-Linux/process.c +++ b/arch/um/os-Linux/process.c @@ -4,6 +4,7 @@ */ #include <stdio.h> +#include <stdlib.h> #include <unistd.h> #include <errno.h> #include <signal.h> @@ -232,6 +233,57 @@ out: return ok; } +static int os_page_mincore(void *addr) +{ + char vec[2]; + int ret; + + ret = mincore(addr, UM_KERN_PAGE_SIZE, vec); + if (ret < 0) { + if (errno == ENOMEM || errno == EINVAL) + return 0; + else + return -errno; + } + + return vec[0] & 1; +} + +int os_mincore(void *addr, unsigned long len) +{ + char *vec; + int ret, i; + + if (len <= UM_KERN_PAGE_SIZE) + return os_page_mincore(addr); + + vec = calloc(1, (len + UM_KERN_PAGE_SIZE - 1) / UM_KERN_PAGE_SIZE); + if (!vec) + return -ENOMEM; + + ret = mincore(addr, UM_KERN_PAGE_SIZE, vec); + if (ret < 0) { + if (errno == ENOMEM || errno == EINVAL) + ret = 0; + else + ret = -errno; + + goto out; + } + + for (i = 0; i < ((len + UM_KERN_PAGE_SIZE - 1) / UM_KERN_PAGE_SIZE); i++) { + if (!(vec[i] & 1)) { + ret = 0; + goto out; + } + } + + ret = 1; +out: + free(vec); + return ret; +} + void init_new_thread_signals(void) { set_handler(SIGSEGV); |