Recently the handling of PR_SET_MM_x been removed because we wanted to improve locking scheme over mm::arg_start,arg_end and etc. Thus to reduce code modification the old PR_SET_MM_x operations have been removed (since initially they've been introduced for c/r sole sake). Before making remove I googled if there are some users of this interface exist and happened to miss that at least systemd is already using PR_SET_MM_ARG_START and PR_SET_MM_ARG_END (see src/basic/process-util.c)
Also Jonathan pointed me that there is a need for sole PR_SET_MM_x operations. https://lkml.org/lkml/2018/5/6/127 Here is a trick: since prctl_set_mm_map now accepts struct prctl_mm_map as an argument we can fetch current mm settings, modify the member requested and send the map into prctl_set_mm_map directly, which simply gonna be like an emulation of PR_SET_MM_MAP. Thus users of PR_SET_MM_x should be able to continue utilizing the interface. CC: Jonathan de Boyne Pollard <[email protected]> CC: Andrey Vagin <[email protected]> CC: Andrew Morton <[email protected]> CC: Michael Kerrisk <[email protected]> CC: Yang Shi <[email protected]> CC: Michal Hocko <[email protected]> Signed-off-by: Cyrill Gorcunov <[email protected]> --- kernel/sys.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 57 insertions(+), 8 deletions(-) Index: linux-ml.git/kernel/sys.c =================================================================== --- linux-ml.git.orig/kernel/sys.c +++ linux-ml.git/kernel/sys.c @@ -1815,7 +1815,6 @@ SYSCALL_DEFINE1(umask, int, mask) return mask; } -#ifdef CONFIG_CHECKPOINT_RESTORE /* * WARNING: we don't require any capability here so be very careful * in what is allowed for modification from userspace. @@ -2046,19 +2045,36 @@ static int prctl_set_mm_map(struct prctl up_read(&mm->mmap_sem); return 0; } -#endif /* CONFIG_CHECKPOINT_RESTORE */ static int prctl_set_mm(int opt, unsigned long addr, unsigned long arg4, unsigned long arg5) { -#ifdef CONFIG_CHECKPOINT_RESTORE + static const unsigned char offsets[] = { + [PR_SET_MM_START_CODE] = offsetof(struct prctl_mm_map, start_code), + [PR_SET_MM_END_CODE] = offsetof(struct prctl_mm_map, end_code), + [PR_SET_MM_START_DATA] = offsetof(struct prctl_mm_map, start_data), + [PR_SET_MM_END_DATA] = offsetof(struct prctl_mm_map, end_data), + [PR_SET_MM_START_STACK] = offsetof(struct prctl_mm_map, start_brk), + [PR_SET_MM_START_BRK] = offsetof(struct prctl_mm_map, brk), + [PR_SET_MM_BRK] = offsetof(struct prctl_mm_map, start_stack), + [PR_SET_MM_ARG_START] = offsetof(struct prctl_mm_map, arg_start), + [PR_SET_MM_ARG_END] = offsetof(struct prctl_mm_map, arg_end), + [PR_SET_MM_ENV_START] = offsetof(struct prctl_mm_map, env_start), + [PR_SET_MM_ENV_END] = offsetof(struct prctl_mm_map, env_end), + }; + struct prctl_mm_map prctl_map = { .exe_fd = (u32)-1, }; + struct mm_struct *mm = current->mm; + + if (arg5 || (arg4 && (opt != PR_SET_MM_AUXV && + opt != PR_SET_MM_MAP && + opt != PR_SET_MM_MAP_SIZE))) + return -EINVAL; + if (opt == PR_SET_MM_MAP_SIZE) return put_user((unsigned int)sizeof(struct prctl_mm_map), (unsigned int __user *)addr); if (opt == PR_SET_MM_MAP) { - struct prctl_mm_map prctl_map = { .exe_fd = (u32)-1, }; - if (arg4 != sizeof(prctl_map)) return -EINVAL; @@ -2068,10 +2084,43 @@ static int prctl_set_mm(int opt, unsigne return prctl_set_mm_map(&prctl_map); } -#endif - pr_warn_once("PR_SET_MM_* has been removed. Use PR_SET_MM_MAP instead\n"); - return -EINVAL; + if (!capable(CAP_SYS_RESOURCE)) + return -EPERM; + + if (opt == PR_SET_MM_EXE_FILE) + return prctl_set_mm_exe_file(mm, (unsigned int)addr); + + if (opt == PR_SET_MM_AUXV) + return prctl_set_auxv(mm, addr, arg4); + + if (opt < 1 || opt >= ARRAY_SIZE(offsets)) + return -EINVAL; + + /* + * Emulate PR_SET_MM_MAP call by filling with + * current values and setting one field from + * the request. + */ + down_read(&mm->mmap_sem); + spin_lock(&mm->arg_lock); + prctl_map.start_code = mm->start_code; + prctl_map.end_code = mm->end_code; + prctl_map.start_data = mm->start_data; + prctl_map.end_data = mm->end_data; + prctl_map.start_brk = mm->start_brk; + prctl_map.brk = mm->brk; + prctl_map.start_stack = mm->start_stack; + prctl_map.arg_start = mm->arg_start; + prctl_map.arg_end = mm->arg_end; + prctl_map.env_start = mm->env_start; + prctl_map.env_end = mm->env_end; + spin_unlock(&mm->arg_lock); + up_read(&mm->mmap_sem); + + *(unsigned long *)((char *)&prctl_map + offsets[opt]) = addr; + + return prctl_set_mm_map(&prctl_map, opt); } #ifdef CONFIG_CHECKPOINT_RESTORE
