From 1bbc55131e59bd099fdc568d3aa0b42634dbd188 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 2 May 2018 21:26:16 -0400 Subject: procfs: get rid of ancient BS in pid_revalidate() uses First of all, calling pid_revalidate() in the end of /* lookups is *not* about closing any kind of races; that used to be true once upon a time, but these days those comments are actively misleading. Especially since pid_revalidate() doesn't even do d_drop() on failure anymore. It doesn't matter, anyway, since once pid_revalidate() starts returning false, ->d_delete() of those dentries starts saying "don't keep"; they won't get stuck in dcache any longer than they are pinned. These calls cannot be just removed, though - the side effect of pid_revalidate() (updating i_uid/i_gid/etc.) is what we are calling it for here. Let's separate the "update ownership" into a new helper (pid_update_inode()) and use it, both in lookups and in pid_revalidate() itself. The comments in pid_revalidate() are also out of date - they refer to the time when pid_revalidate() used to call d_drop() directly... Signed-off-by: Al Viro --- fs/proc/base.c | 55 ++++++++++++++++++++++++------------------------------- 1 file changed, 24 insertions(+), 31 deletions(-) (limited to 'fs/proc/base.c') diff --git a/fs/proc/base.c b/fs/proc/base.c index eafa39a3a88c..6e0875505898 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1803,15 +1803,22 @@ int pid_getattr(const struct path *path, struct kstat *stat, /* dentry stuff */ /* - * Exceptional case: normally we are not allowed to unhash a busy - * directory. In this case, however, we can do it - no aliasing problems - * due to the way we treat inodes. - * + * Set /... inode ownership (can change due to setuid(), etc.) + */ +void pid_update_inode(struct task_struct *task, struct inode *inode) +{ + task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid); + + inode->i_mode &= ~(S_ISUID | S_ISGID); + security_task_to_inode(task, inode); +} + +/* * Rewrite the inode's ownerships here because the owning task may have * performed a setuid(), etc. * */ -int pid_revalidate(struct dentry *dentry, unsigned int flags) +static int pid_revalidate(struct dentry *dentry, unsigned int flags) { struct inode *inode; struct task_struct *task; @@ -1823,10 +1830,7 @@ int pid_revalidate(struct dentry *dentry, unsigned int flags) task = get_proc_task(inode); if (task) { - task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid); - - inode->i_mode &= ~(S_ISUID | S_ISGID); - security_task_to_inode(task, inode); + pid_update_inode(task, inode); put_task_struct(task); return 1; } @@ -2438,7 +2442,7 @@ static int proc_pident_instantiate(struct inode *dir, inode = proc_pid_make_inode(dir->i_sb, task, p->mode); if (!inode) - goto out; + return -ENOENT; ei = PROC_I(inode); if (S_ISDIR(inode->i_mode)) @@ -2448,13 +2452,10 @@ static int proc_pident_instantiate(struct inode *dir, if (p->fop) inode->i_fop = p->fop; ei->op = p->op; + pid_update_inode(task, inode); d_set_d_op(dentry, &pid_dentry_operations); d_add(dentry, inode); - /* Close the race of the process dying before we return the dentry */ - if (pid_revalidate(dentry, 0)) - return 0; -out: - return -ENOENT; + return 0; } static struct dentry *proc_pident_lookup(struct inode *dir, @@ -3140,22 +3141,18 @@ static int proc_pid_instantiate(struct inode *dir, inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO); if (!inode) - goto out; + return -ENOENT; inode->i_op = &proc_tgid_base_inode_operations; inode->i_fop = &proc_tgid_base_operations; inode->i_flags|=S_IMMUTABLE; set_nlink(inode, nlink_tgid); + pid_update_inode(task, inode); d_set_d_op(dentry, &pid_dentry_operations); - d_add(dentry, inode); - /* Close the race of the process dying before we return the dentry */ - if (pid_revalidate(dentry, 0)) - return 0; -out: - return -ENOENT; + return 0; } struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags) @@ -3434,23 +3431,19 @@ static int proc_task_instantiate(struct inode *dir, { struct inode *inode; inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO); - if (!inode) - goto out; + return -ENOENT; + inode->i_op = &proc_tid_base_inode_operations; inode->i_fop = &proc_tid_base_operations; - inode->i_flags|=S_IMMUTABLE; + inode->i_flags |= S_IMMUTABLE; set_nlink(inode, nlink_tid); + pid_update_inode(task, inode); d_set_d_op(dentry, &pid_dentry_operations); - d_add(dentry, inode); - /* Close the race of the process dying before we return the dentry */ - if (pid_revalidate(dentry, 0)) - return 0; -out: - return -ENOENT; + return 0; } static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags) -- cgit v1.2.3 From 0168b9e38c4213e162b15444c071d4198ff470e8 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 3 May 2018 09:21:05 -0400 Subject: procfs: switch instantiate_t to d_splice_alias() ... and get rid of pointless struct inode *dir argument of those, while we are at it. Signed-off-by: Al Viro --- fs/proc/base.c | 93 +++++++++++++++++++++++++++------------------------------- 1 file changed, 43 insertions(+), 50 deletions(-) (limited to 'fs/proc/base.c') diff --git a/fs/proc/base.c b/fs/proc/base.c index 6e0875505898..de22c2002b38 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1878,8 +1878,8 @@ bool proc_fill_cache(struct file *file, struct dir_context *ctx, struct dentry *child, *dir = file->f_path.dentry; struct qstr qname = QSTR_INIT(name, len); struct inode *inode; - unsigned type; - ino_t ino; + unsigned type = DT_UNKNOWN; + ino_t ino = 1; child = d_hash_and_lookup(dir, &qname); if (!child) { @@ -1888,22 +1888,23 @@ bool proc_fill_cache(struct file *file, struct dir_context *ctx, if (IS_ERR(child)) goto end_instantiate; if (d_in_lookup(child)) { - int err = instantiate(d_inode(dir), child, task, ptr); + struct dentry *res; + res = instantiate(child, task, ptr); d_lookup_done(child); - if (err < 0) { - dput(child); + if (IS_ERR(res)) goto end_instantiate; + if (unlikely(res)) { + dput(child); + child = res; } } } inode = d_inode(child); ino = inode->i_ino; type = inode->i_mode >> 12; +end_instantiate: dput(child); return dir_emit(ctx, name, len, ino, type); - -end_instantiate: - return dir_emit(ctx, name, len, 1, DT_UNKNOWN); } /* @@ -2065,19 +2066,19 @@ static const struct inode_operations proc_map_files_link_inode_operations = { .setattr = proc_setattr, }; -static int -proc_map_files_instantiate(struct inode *dir, struct dentry *dentry, +static struct dentry * +proc_map_files_instantiate(struct dentry *dentry, struct task_struct *task, const void *ptr) { fmode_t mode = (fmode_t)(unsigned long)ptr; struct proc_inode *ei; struct inode *inode; - inode = proc_pid_make_inode(dir->i_sb, task, S_IFLNK | + inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | ((mode & FMODE_READ ) ? S_IRUSR : 0) | ((mode & FMODE_WRITE) ? S_IWUSR : 0)); if (!inode) - return -ENOENT; + return ERR_PTR(-ENOENT); ei = PROC_I(inode); ei->op.proc_get_link = map_files_get_link; @@ -2086,9 +2087,7 @@ proc_map_files_instantiate(struct inode *dir, struct dentry *dentry, inode->i_size = 64; d_set_d_op(dentry, &tid_map_files_dentry_operations); - d_add(dentry, inode); - - return 0; + return d_splice_alias(inode, dentry); } static struct dentry *proc_map_files_lookup(struct inode *dir, @@ -2097,19 +2096,19 @@ static struct dentry *proc_map_files_lookup(struct inode *dir, unsigned long vm_start, vm_end; struct vm_area_struct *vma; struct task_struct *task; - int result; + struct dentry *result; struct mm_struct *mm; - result = -ENOENT; + result = ERR_PTR(-ENOENT); task = get_proc_task(dir); if (!task) goto out; - result = -EACCES; + result = ERR_PTR(-EACCES); if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) goto out_put_task; - result = -ENOENT; + result = ERR_PTR(-ENOENT); if (dname_to_vma_addr(dentry, &vm_start, &vm_end)) goto out_put_task; @@ -2123,7 +2122,7 @@ static struct dentry *proc_map_files_lookup(struct inode *dir, goto out_no_vma; if (vma->vm_file) - result = proc_map_files_instantiate(dir, dentry, task, + result = proc_map_files_instantiate(dentry, task, (void *)(unsigned long)vma->vm_file->f_mode); out_no_vma: @@ -2132,7 +2131,7 @@ out_no_vma: out_put_task: put_task_struct(task); out: - return ERR_PTR(result); + return result; } static const struct inode_operations proc_map_files_inode_operations = { @@ -2433,16 +2432,16 @@ static const struct file_operations proc_pid_set_timerslack_ns_operations = { .release = single_release, }; -static int proc_pident_instantiate(struct inode *dir, - struct dentry *dentry, struct task_struct *task, const void *ptr) +static struct dentry *proc_pident_instantiate(struct dentry *dentry, + struct task_struct *task, const void *ptr) { const struct pid_entry *p = ptr; struct inode *inode; struct proc_inode *ei; - inode = proc_pid_make_inode(dir->i_sb, task, p->mode); + inode = proc_pid_make_inode(dentry->d_sb, task, p->mode); if (!inode) - return -ENOENT; + return ERR_PTR(-ENOENT); ei = PROC_I(inode); if (S_ISDIR(inode->i_mode)) @@ -2454,8 +2453,7 @@ static int proc_pident_instantiate(struct inode *dir, ei->op = p->op; pid_update_inode(task, inode); d_set_d_op(dentry, &pid_dentry_operations); - d_add(dentry, inode); - return 0; + return d_splice_alias(inode, dentry); } static struct dentry *proc_pident_lookup(struct inode *dir, @@ -2463,11 +2461,9 @@ static struct dentry *proc_pident_lookup(struct inode *dir, const struct pid_entry *ents, unsigned int nents) { - int error; struct task_struct *task = get_proc_task(dir); const struct pid_entry *p, *last; - - error = -ENOENT; + struct dentry *res = ERR_PTR(-ENOENT); if (!task) goto out_no_task; @@ -2486,11 +2482,11 @@ static struct dentry *proc_pident_lookup(struct inode *dir, if (p >= last) goto out; - error = proc_pident_instantiate(dir, dentry, task, p); + res = proc_pident_instantiate(dentry, task, p); out: put_task_struct(task); out_no_task: - return ERR_PTR(error); + return res; } static int proc_pident_readdir(struct file *file, struct dir_context *ctx, @@ -3133,15 +3129,14 @@ void proc_flush_task(struct task_struct *task) } } -static int proc_pid_instantiate(struct inode *dir, - struct dentry * dentry, +static struct dentry *proc_pid_instantiate(struct dentry * dentry, struct task_struct *task, const void *ptr) { struct inode *inode; - inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO); + inode = proc_pid_make_inode(dentry->d_sb, task, S_IFDIR | S_IRUGO | S_IXUGO); if (!inode) - return -ENOENT; + return ERR_PTR(-ENOENT); inode->i_op = &proc_tgid_base_inode_operations; inode->i_fop = &proc_tgid_base_operations; @@ -3151,16 +3146,15 @@ static int proc_pid_instantiate(struct inode *dir, pid_update_inode(task, inode); d_set_d_op(dentry, &pid_dentry_operations); - d_add(dentry, inode); - return 0; + return d_splice_alias(inode, dentry); } struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags) { - int result = -ENOENT; struct task_struct *task; unsigned tgid; struct pid_namespace *ns; + struct dentry *result = ERR_PTR(-ENOENT); tgid = name_to_int(&dentry->d_name); if (tgid == ~0U) @@ -3175,10 +3169,10 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsign if (!task) goto out; - result = proc_pid_instantiate(dir, dentry, task, NULL); + result = proc_pid_instantiate(dentry, task, NULL); put_task_struct(task); out: - return ERR_PTR(result); + return result; } /* @@ -3426,13 +3420,13 @@ static const struct inode_operations proc_tid_base_inode_operations = { .setattr = proc_setattr, }; -static int proc_task_instantiate(struct inode *dir, - struct dentry *dentry, struct task_struct *task, const void *ptr) +static struct dentry *proc_task_instantiate(struct dentry *dentry, + struct task_struct *task, const void *ptr) { struct inode *inode; - inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO); + inode = proc_pid_make_inode(dentry->d_sb, task, S_IFDIR | S_IRUGO | S_IXUGO); if (!inode) - return -ENOENT; + return ERR_PTR(-ENOENT); inode->i_op = &proc_tid_base_inode_operations; inode->i_fop = &proc_tid_base_operations; @@ -3442,17 +3436,16 @@ static int proc_task_instantiate(struct inode *dir, pid_update_inode(task, inode); d_set_d_op(dentry, &pid_dentry_operations); - d_add(dentry, inode); - return 0; + return d_splice_alias(inode, dentry); } static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags) { - int result = -ENOENT; struct task_struct *task; struct task_struct *leader = get_proc_task(dir); unsigned tid; struct pid_namespace *ns; + struct dentry *result = ERR_PTR(-ENOENT); if (!leader) goto out_no_task; @@ -3472,13 +3465,13 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry if (!same_thread_group(leader, task)) goto out_drop_task; - result = proc_task_instantiate(dir, dentry, task, NULL); + result = proc_task_instantiate(dentry, task, NULL); out_drop_task: put_task_struct(task); out: put_task_struct(leader); out_no_task: - return ERR_PTR(result); + return result; } /* -- cgit v1.2.3