diff options
| author | Bodo Stroesser <bstroesser@fujitsu-siemens.com> | 2006-03-27 01:14:34 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-27 08:44:38 -0800 |
| commit | 81efcd3300754462537ffac60336158b2f773b4e (patch) | |
| tree | f957ccb8cacabcecf5cfd67c1feda5b1908cac0c /arch/um/sys-i386 | |
| parent | f206aabb035318ac4bafbf0b87798335de3634df (diff) | |
[PATCH] uml: more carefully test whether we are in a system call
For security reasons, UML in is_syscall() needs to have access to code in
vsyscall-page. The current implementation grants this access by explicitly
allowing access to vsyscall in access_ok_skas(). With this change,
copy_from_user() may be used to read the code. Ptrace access to vsyscall-page
for debugging already was implemented in get_user_pages() by mainline. In
i386, copy_from_user can't access vsyscall-page, but returns EFAULT.
To make UML behave as i386 does, I changed is_syscall to use
access_process_vm(current) to read the code from vsyscall-page. This doesn't
hurt security, but simplifies the code and prepares implementation of
stub-vmas.
Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/um/sys-i386')
| -rw-r--r-- | arch/um/sys-i386/ptrace.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/arch/um/sys-i386/ptrace.c b/arch/um/sys-i386/ptrace.c index e839ce65ad2..8032a105949 100644 --- a/arch/um/sys-i386/ptrace.c +++ b/arch/um/sys-i386/ptrace.c @@ -6,6 +6,7 @@ #include <linux/config.h> #include <linux/compiler.h> #include "linux/sched.h" +#include "linux/mm.h" #include "asm/elf.h" #include "asm/ptrace.h" #include "asm/uaccess.h" @@ -26,9 +27,17 @@ int is_syscall(unsigned long addr) n = copy_from_user(&instr, (void __user *) addr, sizeof(instr)); if(n){ - printk("is_syscall : failed to read instruction from 0x%lx\n", - addr); - return(0); + /* access_process_vm() grants access to vsyscall and stub, + * while copy_from_user doesn't. Maybe access_process_vm is + * slow, but that doesn't matter, since it will be called only + * in case of singlestepping, if copy_from_user failed. + */ + n = access_process_vm(current, addr, &instr, sizeof(instr), 0); + if(n != sizeof(instr)) { + printk("is_syscall : failed to read instruction from " + "0x%lx\n", addr); + return(1); + } } /* int 0x80 or sysenter */ return((instr == 0x80cd) || (instr == 0x340f)); |