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Message-ID: <5202251B.2020307@asianux.com>
Date: Wed, 07 Aug 2013 18:44:43 +0800
From: Chen Gang <gang.chen@...anux.com>
To: Kees Cook <keescook@...omium.org>,
Al Viro <viro@...iv.linux.org.uk>,
Oleg Nesterov <oleg@...hat.com>, holt@....com
CC: Andrew Morton <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel/sys.c: improve the usage of return value
According to the related discussion in another thread, this patch can be
obsoleted now.
Thanks.
On 08/06/2013 04:43 PM, Chen Gang wrote:
> Improve the usage of return value, so not only can make code clearer
> to readers, but also can improve the performance.
>
> Assign the return error code only when error occurs, so can save some
> instructions.
>
> For getcpu(), uname(), newuname(), and override_release(), can remove
> the return variable to make code clearer and save some instructions.
>
> Also modify the related code to pass "./scripts/checkpatch.pl" checking.
>
>
> Signed-off-by: Chen Gang <gang.chen@...anux.com>
> ---
> kernel/sys.c | 147 +++++++++++++++++++++++++++++++---------------------------
> 1 files changed, 79 insertions(+), 68 deletions(-)
>
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 771129b..a63a350 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -386,13 +386,14 @@ SYSCALL_DEFINE1(setgid, gid_t, gid)
> return -ENOMEM;
> old = current_cred();
>
> - retval = -EPERM;
> if (nsown_capable(CAP_SETGID))
> new->gid = new->egid = new->sgid = new->fsgid = kgid;
> else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid))
> new->egid = new->fsgid = kgid;
> - else
> + else {
> + retval = -EPERM;
> goto error;
> + }
>
> return commit_creds(new);
>
> @@ -533,7 +534,6 @@ SYSCALL_DEFINE1(setuid, uid_t, uid)
> return -ENOMEM;
> old = current_cred();
>
> - retval = -EPERM;
> if (nsown_capable(CAP_SETUID)) {
> new->suid = new->uid = kuid;
> if (!uid_eq(kuid, old->uid)) {
> @@ -542,6 +542,7 @@ SYSCALL_DEFINE1(setuid, uid_t, uid)
> goto error;
> }
> } else if (!uid_eq(kuid, old->uid) && !uid_eq(kuid, new->suid)) {
> + retval = -EPERM;
> goto error;
> }
>
> @@ -919,31 +920,35 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)
> */
> write_lock_irq(&tasklist_lock);
>
> - err = -ESRCH;
> p = find_task_by_vpid(pid);
> - if (!p)
> + if (!p) {
> + err = -ESRCH;
> goto out;
> + }
>
> - err = -EINVAL;
> - if (!thread_group_leader(p))
> + if (!thread_group_leader(p)) {
> + err = -EINVAL;
> goto out;
> + }
>
> if (same_thread_group(p->real_parent, group_leader)) {
> - err = -EPERM;
> - if (task_session(p) != task_session(group_leader))
> + if (task_session(p) != task_session(group_leader)) {
> + err = -EPERM;
> goto out;
> - err = -EACCES;
> - if (p->did_exec)
> + }
> + if (p->did_exec) {
> + err = -EACCES;
> goto out;
> - } else {
> + }
> + } else if (p != group_leader) {
> err = -ESRCH;
> - if (p != group_leader)
> - goto out;
> + goto out;
> }
>
> - err = -EPERM;
> - if (p->signal->leader)
> + if (p->signal->leader) {
> + err = -EPERM;
> goto out;
> + }
>
> pgrp = task_pid(p);
> if (pgid != pid) {
> @@ -951,8 +956,10 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)
>
> pgrp = find_vpid(pgid);
> g = pid_task(pgrp, PIDTYPE_PGID);
> - if (!g || task_session(g) != task_session(group_leader))
> + if (!g || task_session(g) != task_session(group_leader)) {
> + err = -EPERM;
> goto out;
> + }
> }
>
> err = security_task_setpgid(p, pgid);
> @@ -962,7 +969,6 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)
> if (task_pgrp(p) != pgrp)
> change_pid(p, PIDTYPE_PGID, pgrp);
>
> - err = 0;
> out:
> /* All paths lead to here, thus we are safe. -DaveM */
> write_unlock_irq(&tasklist_lock);
> @@ -980,14 +986,16 @@ SYSCALL_DEFINE1(getpgid, pid_t, pid)
> if (!pid)
> grp = task_pgrp(current);
> else {
> - retval = -ESRCH;
> p = find_task_by_vpid(pid);
> - if (!p)
> + if (!p) {
> + retval = -ESRCH;
> goto out;
> + }
> grp = task_pgrp(p);
> - if (!grp)
> + if (!grp) {
> + retval = -ESRCH;
> goto out;
> -
> + }
> retval = security_task_getpgid(p);
> if (retval)
> goto out;
> @@ -1017,14 +1025,16 @@ SYSCALL_DEFINE1(getsid, pid_t, pid)
> if (!pid)
> sid = task_session(current);
> else {
> - retval = -ESRCH;
> p = find_task_by_vpid(pid);
> - if (!p)
> + if (!p) {
> + retval = -ESRCH;
> goto out;
> + }
> sid = task_session(p);
> - if (!sid)
> + if (!sid) {
> + retval = -ESRCH;
> goto out;
> -
> + }
> retval = security_task_getsid(p);
> if (retval)
> goto out;
> @@ -1096,8 +1106,6 @@ DECLARE_RWSEM(uts_sem);
> */
> static int override_release(char __user *release, size_t len)
> {
> - int ret = 0;
> -
> if (current->personality & UNAME26) {
> const char *rest = UTS_RELEASE;
> char buf[65] = { 0 };
> @@ -1115,25 +1123,25 @@ static int override_release(char __user *release, size_t len)
> v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;
> copy = clamp_t(size_t, len, 1, sizeof(buf));
> copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
> - ret = copy_to_user(release, buf, copy + 1);
> + return copy_to_user(release, buf, copy + 1);
> }
> - return ret;
> + return 0;
> }
>
> SYSCALL_DEFINE1(newuname, struct new_utsname __user *, name)
> {
> - int errno = 0;
> -
> down_read(&uts_sem);
> - if (copy_to_user(name, utsname(), sizeof *name))
> - errno = -EFAULT;
> + if (copy_to_user(name, utsname(), sizeof(*name))) {
> + up_read(&uts_sem);
> + return -EFAULT;
> + }
> up_read(&uts_sem);
>
> - if (!errno && override_release(name->release, sizeof(name->release)))
> - errno = -EFAULT;
> - if (!errno && override_architecture(name))
> - errno = -EFAULT;
> - return errno;
> + if (override_release(name->release, sizeof(name->release)))
> + return -EFAULT;
> + if (override_architecture(name))
> + return -EFAULT;
> + return 0;
> }
>
> #ifdef __ARCH_WANT_SYS_OLD_UNAME
> @@ -1142,21 +1150,21 @@ SYSCALL_DEFINE1(newuname, struct new_utsname __user *, name)
> */
> SYSCALL_DEFINE1(uname, struct old_utsname __user *, name)
> {
> - int error = 0;
> -
> if (!name)
> return -EFAULT;
>
> down_read(&uts_sem);
> - if (copy_to_user(name, utsname(), sizeof(*name)))
> - error = -EFAULT;
> + if (copy_to_user(name, utsname(), sizeof(*name))) {
> + up_read(&uts_sem);
> + return -EFAULT;
> + }
> up_read(&uts_sem);
>
> - if (!error && override_release(name->release, sizeof(name->release)))
> - error = -EFAULT;
> - if (!error && override_architecture(name))
> - error = -EFAULT;
> - return error;
> + if (override_release(name->release, sizeof(name->release)))
> + return -EFAULT;
> + if (override_architecture(name))
> + return -EFAULT;
> + return 0;
> }
>
> SYSCALL_DEFINE1(olduname, struct oldold_utsname __user *, name)
> @@ -1185,12 +1193,14 @@ SYSCALL_DEFINE1(olduname, struct oldold_utsname __user *, name)
> __OLD_UTS_LEN);
> error |= __put_user(0, name->machine + __OLD_UTS_LEN);
> up_read(&uts_sem);
> + if (error)
> + return -EFAULT;
>
> - if (!error && override_architecture(name))
> - error = -EFAULT;
> - if (!error && override_release(name->release, sizeof(name->release)))
> - error = -EFAULT;
> - return error ? -EFAULT : 0;
> + if (override_architecture(name))
> + return -EFAULT;
> + if (override_release(name->release, sizeof(name->release)))
> + return -EFAULT;
> + return 0;
> }
> #endif
>
> @@ -1648,10 +1658,11 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
> * sure that this one is executable as well, to avoid breaking an
> * overall picture.
> */
> - err = -EACCES;
> - if (!S_ISREG(inode->i_mode) ||
> - exe.file->f_path.mnt->mnt_flags & MNT_NOEXEC)
> + if (!S_ISREG(inode->i_mode) ||
> + exe.file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
> + err = -EACCES;
> goto exit;
> + }
>
> err = inode_permission(inode, MAY_EXEC);
> if (err)
> @@ -1662,15 +1673,16 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
> /*
> * Forbid mm->exe_file change if old file still mapped.
> */
> - err = -EBUSY;
> if (mm->exe_file) {
> struct vm_area_struct *vma;
>
> for (vma = mm->mmap; vma; vma = vma->vm_next)
> if (vma->vm_file &&
> path_equal(&vma->vm_file->f_path,
> - &mm->exe_file->f_path))
> + &mm->exe_file->f_path)) {
> + err = -EBUSY;
> goto exit_unlock;
> + }
> }
>
> /*
> @@ -1679,11 +1691,10 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
> * could make a snapshot over all processes running and monitor
> * /proc/pid/exe changes to notice unusual activity if needed.
> */
> - err = -EPERM;
> - if (test_and_set_bit(MMF_EXE_FILE_CHANGED, &mm->flags))
> + if (test_and_set_bit(MMF_EXE_FILE_CHANGED, &mm->flags)) {
> + err = -EPERM;
> goto exit_unlock;
> -
> - err = 0;
> + }
> set_mm_exe_file(mm, exe.file); /* this grabs a reference to exe.file */
> exit_unlock:
> up_write(&mm->mmap_sem);
> @@ -2009,13 +2020,13 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
> SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep,
> struct getcpu_cache __user *, unused)
> {
> - int err = 0;
> int cpu = raw_smp_processor_id();
> - if (cpup)
> - err |= put_user(cpu, cpup);
> - if (nodep)
> - err |= put_user(cpu_to_node(cpu), nodep);
> - return err ? -EFAULT : 0;
> +
> + if (cpup && put_user(cpu, cpup))
> + return -EFAULT;
> + if (nodep && put_user(cpu_to_node(cpu), nodep))
> + return -EFAULT;
> + return 0;
> }
>
> /**
>
--
Chen Gang
--
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