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![Roland McGrath](/assets/img/avatar_default.png)
The prevent_tail_call() macro works around the problem of the compiler clobbering argument words on the stack, which for asmlinkage functions is the caller's (user's) struct pt_regs. The tail/sibling-call optimization is not the only way that the compiler can decide to use stack argument words as scratch space, which we have to prevent. Other optimizations can do it too. Until we have new compiler support to make "asmlinkage" binding on the compiler's own use of the stack argument frame, we have work around all the manifestations of this issue that crop up. More cases seem to be prevented by also keeping the incoming argument variables live at the end of the function. This makes their original stack slots attractive places to leave those variables, so the compiler tends not clobber them for something else. It's still no guarantee, but it handles some observed cases that prevent_tail_call() did not. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
229 lines
5.3 KiB
C
229 lines
5.3 KiB
C
/*
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* Wrapper functions for 16bit uid back compatibility. All nicely tied
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* together in the faint hope we can take the out in five years time.
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*/
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#include <linux/mm.h>
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#include <linux/utsname.h>
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#include <linux/mman.h>
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#include <linux/notifier.h>
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#include <linux/reboot.h>
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#include <linux/prctl.h>
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#include <linux/capability.h>
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#include <linux/init.h>
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#include <linux/highuid.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <asm/uaccess.h>
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asmlinkage long sys_chown16(const char __user * filename, old_uid_t user, old_gid_t group)
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{
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long ret = sys_chown(filename, low2highuid(user), low2highgid(group));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(3, ret, filename, user, group);
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return ret;
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}
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asmlinkage long sys_lchown16(const char __user * filename, old_uid_t user, old_gid_t group)
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{
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long ret = sys_lchown(filename, low2highuid(user), low2highgid(group));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(3, ret, filename, user, group);
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return ret;
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}
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asmlinkage long sys_fchown16(unsigned int fd, old_uid_t user, old_gid_t group)
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{
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long ret = sys_fchown(fd, low2highuid(user), low2highgid(group));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(3, ret, fd, user, group);
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return ret;
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}
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asmlinkage long sys_setregid16(old_gid_t rgid, old_gid_t egid)
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{
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long ret = sys_setregid(low2highgid(rgid), low2highgid(egid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(2, ret, rgid, egid);
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return ret;
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}
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asmlinkage long sys_setgid16(old_gid_t gid)
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{
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long ret = sys_setgid(low2highgid(gid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(1, ret, gid);
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return ret;
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}
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asmlinkage long sys_setreuid16(old_uid_t ruid, old_uid_t euid)
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{
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long ret = sys_setreuid(low2highuid(ruid), low2highuid(euid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(2, ret, ruid, euid);
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return ret;
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}
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asmlinkage long sys_setuid16(old_uid_t uid)
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{
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long ret = sys_setuid(low2highuid(uid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(1, ret, uid);
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return ret;
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}
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asmlinkage long sys_setresuid16(old_uid_t ruid, old_uid_t euid, old_uid_t suid)
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{
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long ret = sys_setresuid(low2highuid(ruid), low2highuid(euid),
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low2highuid(suid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(3, ret, ruid, euid, suid);
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return ret;
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}
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asmlinkage long sys_getresuid16(old_uid_t __user *ruid, old_uid_t __user *euid, old_uid_t __user *suid)
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{
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int retval;
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if (!(retval = put_user(high2lowuid(current->uid), ruid)) &&
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!(retval = put_user(high2lowuid(current->euid), euid)))
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retval = put_user(high2lowuid(current->suid), suid);
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return retval;
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}
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asmlinkage long sys_setresgid16(old_gid_t rgid, old_gid_t egid, old_gid_t sgid)
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{
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long ret = sys_setresgid(low2highgid(rgid), low2highgid(egid),
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low2highgid(sgid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(3, ret, rgid, egid, sgid);
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return ret;
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}
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asmlinkage long sys_getresgid16(old_gid_t __user *rgid, old_gid_t __user *egid, old_gid_t __user *sgid)
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{
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int retval;
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if (!(retval = put_user(high2lowgid(current->gid), rgid)) &&
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!(retval = put_user(high2lowgid(current->egid), egid)))
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retval = put_user(high2lowgid(current->sgid), sgid);
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return retval;
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}
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asmlinkage long sys_setfsuid16(old_uid_t uid)
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{
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long ret = sys_setfsuid(low2highuid(uid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(1, ret, uid);
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return ret;
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}
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asmlinkage long sys_setfsgid16(old_gid_t gid)
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{
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long ret = sys_setfsgid(low2highgid(gid));
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/* avoid REGPARM breakage on x86: */
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asmlinkage_protect(1, ret, gid);
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return ret;
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}
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static int groups16_to_user(old_gid_t __user *grouplist,
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struct group_info *group_info)
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{
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int i;
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old_gid_t group;
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for (i = 0; i < group_info->ngroups; i++) {
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group = high2lowgid(GROUP_AT(group_info, i));
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if (put_user(group, grouplist+i))
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return -EFAULT;
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}
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return 0;
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}
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static int groups16_from_user(struct group_info *group_info,
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old_gid_t __user *grouplist)
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{
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int i;
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old_gid_t group;
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for (i = 0; i < group_info->ngroups; i++) {
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if (get_user(group, grouplist+i))
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return -EFAULT;
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GROUP_AT(group_info, i) = low2highgid(group);
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}
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return 0;
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}
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asmlinkage long sys_getgroups16(int gidsetsize, old_gid_t __user *grouplist)
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{
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int i = 0;
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if (gidsetsize < 0)
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return -EINVAL;
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get_group_info(current->group_info);
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i = current->group_info->ngroups;
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if (gidsetsize) {
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if (i > gidsetsize) {
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i = -EINVAL;
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goto out;
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}
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if (groups16_to_user(grouplist, current->group_info)) {
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i = -EFAULT;
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goto out;
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}
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}
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out:
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put_group_info(current->group_info);
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return i;
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}
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asmlinkage long sys_setgroups16(int gidsetsize, old_gid_t __user *grouplist)
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{
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struct group_info *group_info;
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int retval;
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if (!capable(CAP_SETGID))
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return -EPERM;
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if ((unsigned)gidsetsize > NGROUPS_MAX)
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return -EINVAL;
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group_info = groups_alloc(gidsetsize);
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if (!group_info)
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return -ENOMEM;
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retval = groups16_from_user(group_info, grouplist);
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if (retval) {
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put_group_info(group_info);
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return retval;
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}
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retval = set_current_groups(group_info);
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put_group_info(group_info);
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return retval;
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}
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asmlinkage long sys_getuid16(void)
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{
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return high2lowuid(current->uid);
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}
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asmlinkage long sys_geteuid16(void)
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{
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return high2lowuid(current->euid);
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}
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asmlinkage long sys_getgid16(void)
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{
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return high2lowgid(current->gid);
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}
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asmlinkage long sys_getegid16(void)
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{
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return high2lowgid(current->egid);
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}
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