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![Alexey Dobriyan](/assets/img/avatar_default.png)
Current supplementary groups code can massively overallocate memory and is implemented in a way so that access to individual gid is done via 2D array. If number of gids is <= 32, memory allocation is more or less tolerable (140/148 bytes). But if it is not, code allocates full page (!) regardless and, what's even more fun, doesn't reuse small 32-entry array. 2D array means dependent shifts, loads and LEAs without possibility to optimize them (gid is never known at compile time). All of the above is unnecessary. Switch to the usual trailing-zero-len-array scheme. Memory is allocated with kmalloc/vmalloc() and only as much as needed. Accesses become simpler (LEA 8(gi,idx,4) or even without displacement). Maximum number of gids is 65536 which translates to 256KB+8 bytes. I think kernel can handle such allocation. On my usual desktop system with whole 9 (nine) aux groups, struct group_info shrinks from 148 bytes to 44 bytes, yay! Nice side effects: - "gi->gid[i]" is shorter than "GROUP_AT(gi, i)", less typing, - fix little mess in net/ipv4/ping.c should have been using GROUP_AT macro but this point becomes moot, - aux group allocation is persistent and should be accounted as such. Link: http://lkml.kernel.org/r/20160817201927.GA2096@p183.telecom.by Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Vasily Kulikov <segoon@openwall.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
217 lines
5 KiB
C
217 lines
5 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/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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SYSCALL_DEFINE3(chown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
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{
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return sys_chown(filename, low2highuid(user), low2highgid(group));
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}
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SYSCALL_DEFINE3(lchown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
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{
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return sys_lchown(filename, low2highuid(user), low2highgid(group));
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}
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SYSCALL_DEFINE3(fchown16, unsigned int, fd, old_uid_t, user, old_gid_t, group)
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{
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return sys_fchown(fd, low2highuid(user), low2highgid(group));
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}
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SYSCALL_DEFINE2(setregid16, old_gid_t, rgid, old_gid_t, egid)
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{
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return sys_setregid(low2highgid(rgid), low2highgid(egid));
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}
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SYSCALL_DEFINE1(setgid16, old_gid_t, gid)
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{
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return sys_setgid(low2highgid(gid));
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}
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SYSCALL_DEFINE2(setreuid16, old_uid_t, ruid, old_uid_t, euid)
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{
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return sys_setreuid(low2highuid(ruid), low2highuid(euid));
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}
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SYSCALL_DEFINE1(setuid16, old_uid_t, uid)
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{
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return sys_setuid(low2highuid(uid));
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}
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SYSCALL_DEFINE3(setresuid16, old_uid_t, ruid, old_uid_t, euid, old_uid_t, suid)
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{
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return sys_setresuid(low2highuid(ruid), low2highuid(euid),
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low2highuid(suid));
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}
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SYSCALL_DEFINE3(getresuid16, old_uid_t __user *, ruidp, old_uid_t __user *, euidp, old_uid_t __user *, suidp)
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{
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const struct cred *cred = current_cred();
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int retval;
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old_uid_t ruid, euid, suid;
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ruid = high2lowuid(from_kuid_munged(cred->user_ns, cred->uid));
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euid = high2lowuid(from_kuid_munged(cred->user_ns, cred->euid));
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suid = high2lowuid(from_kuid_munged(cred->user_ns, cred->suid));
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if (!(retval = put_user(ruid, ruidp)) &&
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!(retval = put_user(euid, euidp)))
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retval = put_user(suid, suidp);
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return retval;
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}
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SYSCALL_DEFINE3(setresgid16, old_gid_t, rgid, old_gid_t, egid, old_gid_t, sgid)
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{
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return sys_setresgid(low2highgid(rgid), low2highgid(egid),
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low2highgid(sgid));
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}
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SYSCALL_DEFINE3(getresgid16, old_gid_t __user *, rgidp, old_gid_t __user *, egidp, old_gid_t __user *, sgidp)
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{
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const struct cred *cred = current_cred();
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int retval;
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old_gid_t rgid, egid, sgid;
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rgid = high2lowgid(from_kgid_munged(cred->user_ns, cred->gid));
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egid = high2lowgid(from_kgid_munged(cred->user_ns, cred->egid));
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sgid = high2lowgid(from_kgid_munged(cred->user_ns, cred->sgid));
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if (!(retval = put_user(rgid, rgidp)) &&
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!(retval = put_user(egid, egidp)))
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retval = put_user(sgid, sgidp);
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return retval;
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}
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SYSCALL_DEFINE1(setfsuid16, old_uid_t, uid)
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{
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return sys_setfsuid(low2highuid(uid));
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}
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SYSCALL_DEFINE1(setfsgid16, old_gid_t, gid)
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{
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return sys_setfsgid(low2highgid(gid));
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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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struct user_namespace *user_ns = current_user_ns();
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int i;
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old_gid_t group;
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kgid_t kgid;
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for (i = 0; i < group_info->ngroups; i++) {
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kgid = group_info->gid[i];
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group = high2lowgid(from_kgid_munged(user_ns, kgid));
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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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struct user_namespace *user_ns = current_user_ns();
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int i;
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old_gid_t group;
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kgid_t kgid;
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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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kgid = make_kgid(user_ns, low2highgid(group));
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if (!gid_valid(kgid))
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return -EINVAL;
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group_info->gid[i] = kgid;
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}
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return 0;
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}
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SYSCALL_DEFINE2(getgroups16, int, gidsetsize, old_gid_t __user *, grouplist)
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{
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const struct cred *cred = current_cred();
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int i;
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if (gidsetsize < 0)
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return -EINVAL;
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i = cred->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, cred->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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return i;
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}
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SYSCALL_DEFINE2(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 (!may_setgroups())
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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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SYSCALL_DEFINE0(getuid16)
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{
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return high2lowuid(from_kuid_munged(current_user_ns(), current_uid()));
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}
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SYSCALL_DEFINE0(geteuid16)
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{
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return high2lowuid(from_kuid_munged(current_user_ns(), current_euid()));
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}
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SYSCALL_DEFINE0(getgid16)
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{
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return high2lowgid(from_kgid_munged(current_user_ns(), current_gid()));
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}
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SYSCALL_DEFINE0(getegid16)
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{
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return high2lowgid(from_kgid_munged(current_user_ns(), current_egid()));
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}
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