Messages in this thread Patch in this message | | | Date | Wed, 29 Feb 2012 19:16:34 +0400 | From | Cyrill Gorcunov <> | Subject | [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file |
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Hi guys,
at restore time we would like to have a way for /proc/pid/exe symlink recovering. So I thought extending prctl might be a good idea.
Still maybe there some other good and 'right' way to do it, so I would like to gather opinions.
Please review, thanks!
Cyrill --- From: Cyrill Gorcunov <gorcunov@openvz.org> Subject: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file
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.
Note, if mm_struct::exe_file already mapped more than once we refuse to change anything (which prevents kernel from potential problems).
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> --- include/linux/prctl.h | 1 kernel/sys.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 73 insertions(+), 1 deletion(-)
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 @@ -1701,6 +1701,66 @@ static bool vma_flags_mismatch(struct vm (vma->vm_flags & banned); } +/* Expects mm->mmap_sem is read-taken */ +static int prctl_set_mm_exe_file(struct mm_struct *mm, + const void __user *path, + size_t size) +{ + struct file *new_exe_file; + char *pathbuf; + int ret = 0; + + if (size >= PATH_MAX) + return -EINVAL; + + /* + * We allow to change only those exe's which + * are not mapped several times. This one + * is early test while mmap_sem is taken. + */ + if (mm->num_exe_file_vmas > 1) + return -EBUSY; + + up_read(&mm->mmap_sem); + + pathbuf = kmalloc(size, GFP_TEMPORARY); + if (!pathbuf) { + ret = -ENOMEM; + goto err_down; + } + + if (copy_from_user(pathbuf, path, size)) { + kfree(pathbuf); + ret = -EFAULT; + goto err_down; + } + pathbuf[size-1] = '\0'; + + new_exe_file = open_exec(pathbuf); + kfree(pathbuf); + + down_read(&mm->mmap_sem); + + if (IS_ERR(new_exe_file)) + return PTR_ERR(new_exe_file); + + /* + * We allow to change only those exe's which + * are not mapped several times. + */ + if (mm->num_exe_file_vmas < 2) { + set_mm_exe_file(mm, new_exe_file); + ret = 0; + } else + ret = -EBUSY; + + return ret; + +err_down: + down_read(&mm->mmap_sem); + return ret; +} + static int prctl_set_mm(int opt, unsigned long addr, unsigned long arg4, unsigned long arg5) { @@ -1709,7 +1769,9 @@ static int prctl_set_mm(int opt, unsigne struct vm_area_struct *vma; int error = 0; - if (arg5 || (arg4 && opt != PR_SET_MM_AUXV)) + if (arg5 || (arg4 && + opt != PR_SET_MM_AUXV && + opt != PR_SET_MM_EXE_FILE)) return -EINVAL; if (!capable(CAP_SYS_ADMIN)) @@ -1837,6 +1899,15 @@ static int prctl_set_mm(int opt, unsigne return 0; } + + /* + * This to restore /proc/self/exe link. + */ + case PR_SET_MM_EXE_FILE: + error = prctl_set_mm_exe_file(mm, (const void __user *)addr, arg4); + if (error) + goto out; + break; default: error = -EINVAL; goto out;
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