| From stable-bounces@linux.kernel.org Fri Mar 23 12:41:21 2007 |
| From: Jeff Dike <jdike@addtoit.com> |
| Date: Fri, 23 Mar 2007 15:37:30 -0400 |
| Subject: UML - host VDSO fix |
| To: stable@kernel.org |
| Cc: uml-devel <user-mode-linux-devel@lists.sourceforge.net> |
| Message-ID: <20070323193730.GA9519@c2.user-mode-linux.org> |
| Content-Disposition: inline |
| |
| From: Jeff Dike <jdike@addtoit.com> |
| |
| This fixes a problem seen by a number of people running UML on newer host |
| kernels. init would hang with an infinite segfault loop. |
| |
| It turns out that the host kernel was providing a AT_SYSINFO_EHDR of |
| 0xffffe000, which faked UML into believing that the host VDSO page could be |
| reused. However, AT_SYSINFO pointed into the middle of the address space, and |
| was unmapped as a result. Because UML was providing AT_SYSINFO_EHDR and |
| AT_SYSINFO to its own processes, these would branch to nowhere when trying to |
| use the VDSO. |
| |
| The fix is to also check the location of AT_SYSINFO when deciding whether to |
| use the host's VDSO. |
| |
| Signed-off-by: Jeff Dike <jdike@linux.intel.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| arch/um/os-Linux/elf_aux.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| --- a/arch/um/os-Linux/elf_aux.c |
| +++ b/arch/um/os-Linux/elf_aux.c |
| @@ -40,6 +40,9 @@ __init void scan_elf_aux( char **envp) |
| switch ( auxv->a_type ) { |
| case AT_SYSINFO: |
| __kernel_vsyscall = auxv->a_un.a_val; |
| + /* See if the page is under TASK_SIZE */ |
| + if (__kernel_vsyscall < (unsigned long) envp) |
| + __kernel_vsyscall = 0; |
| break; |
| case AT_SYSINFO_EHDR: |
| vsyscall_ehdr = auxv->a_un.a_val; |
