Messages in this thread Patch in this message | | | Date | Fri, 2 Mar 2012 18:26:30 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file |
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On Thu, Mar 01, 2012 at 08:41:20PM +0100, Oleg Nesterov wrote: ... > Still can't understand. I think you need: > > file = fget(fd); > if (!file) > return -EBADF; > > down_write(&mm->mmap_sem); > if (mm->num_exe_file_vmas) { > fput(mm->exe_file); > mm->exe_file = file; > file = NULL; > } > up_write(&mm->mmap_sem); > > if (!file) > return 0; > > fput(file); > return -ESOMETHING; > > and that is all.
Hi Oleg, sure you were right. I even think testing for num_exe_file_vmas is not needed, since until real executable VMA is read and mapped it might remain zero. So I guess something like below should work.
Cyrill --- From: Cyrill Gorcunov <gorcunov@openvz.org> Subject: c/r: prctl: Add ability to set new mm_struct::exe_file v2
When we do restore we would like to have a way to setup a former mm_struct::exe_file so that /proc/pid/exe would point to the original executable file a process had at checkpoint time.
For this sake PR_SET_MM_EXE_FILE code is introduced.
This feature is available iif CONFIG_CHECKPOINT_RESTORE is set.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> CC: Oleg Nesterov <oleg@redhat.com> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> CC: Pavel Emelyanov <xemul@parallels.com> CC: Kees Cook <keescook@chromium.org> CC: Tejun Heo <tj@kernel.org> --- include/linux/prctl.h | 1 + kernel/sys.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+)
Index: linux-2.6.git/include/linux/prctl.h =================================================================== --- linux-2.6.git.orig/include/linux/prctl.h +++ linux-2.6.git/include/linux/prctl.h @@ -118,5 +118,6 @@ # define PR_SET_MM_ENV_START 10 # define PR_SET_MM_ENV_END 11 # define PR_SET_MM_AUXV 12 +# define PR_SET_MM_EXE_FILE 13 #endif /* _LINUX_PRCTL_H */ Index: linux-2.6.git/kernel/sys.c =================================================================== --- linux-2.6.git.orig/kernel/sys.c +++ linux-2.6.git/kernel/sys.c @@ -36,6 +36,7 @@ #include <linux/personality.h> #include <linux/ptrace.h> #include <linux/fs_struct.h> +#include <linux/file.h> #include <linux/gfp.h> #include <linux/syscore_ops.h> #include <linux/version.h> @@ -1701,6 +1702,25 @@ static bool vma_flags_mismatch(struct vm (vma->vm_flags & banned); } +static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd) +{ + struct file *new_exe_file, *old_exe_file; + + new_exe_file = fget(fd); + if (!new_exe_file) + return -EBADF; + + down_write(&mm->mmap_sem); + old_exe_file = mm->exe_file; + mm->exe_file = new_exe_file; + up_write(&mm->mmap_sem); + + if (old_exe_file) + fput(old_exe_file); + + return 0; +} + static int prctl_set_mm(int opt, unsigned long addr, unsigned long arg4, unsigned long arg5) { @@ -1715,6 +1735,9 @@ static int prctl_set_mm(int opt, unsigne if (!capable(CAP_SYS_ADMIN)) return -EPERM; + if (opt == PR_SET_MM_EXE_FILE) + return prctl_set_mm_exe_file(mm, (unsigned int)addr); + if (addr >= TASK_SIZE) return -EINVAL; @@ -1837,6 +1860,7 @@ static int prctl_set_mm(int opt, unsigne return 0; } + default: error = -EINVAL; goto out;
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