From 29a40ace841cba9b661711f042d1821cdc4ad47c Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 9 Oct 2014 15:25:26 -0700 Subject: fs/proc/task_mmu.c: shift mm_access() from m_start() to proc_maps_open() A simple test-case from Kirill Shutemov cat /proc/self/maps >/dev/null chmod +x /proc/self/net/packet exec /proc/self/net/packet makes lockdep unhappy, cat/exec take seq_file->lock + cred_guard_mutex in the opposite order. It's a false positive and probably we should not allow "chmod +x" on proc files. Still I think that we should avoid mm_access() and cred_guard_mutex in sys_read() paths, security checking should happen at open time. Besides, this doesn't even look right if the task changes its ->mm between m_stop() and m_start(). Add the new "mm_struct *mm" member into struct proc_maps_private and change proc_maps_open() to initialize it using proc_mem_open(). Change m_start() to use priv->mm if atomic_inc_not_zero(mm_users) succeeds or return NULL (eof) otherwise. The only complication is that proc_maps_open() users should additionally do mmdrop() in fop->release(), add the new proc_map_release() helper for that. Note: this is the user-visible change, if the task execs after open("maps") the new ->mm won't be visible via this file. I hope this is fine, and this matches /proc/pid/mem bahaviour. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Oleg Nesterov Reported-by: "Kirill A. Shutemov" Acked-by: Kirill A. Shutemov Acked-by: Cyrill Gorcunov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) (limited to 'fs/proc/task_mmu.c') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 4d716a09d500..a1454dac7e0a 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -165,9 +165,9 @@ static void *m_start(struct seq_file *m, loff_t *pos) if (!priv->task) return ERR_PTR(-ESRCH); - mm = mm_access(priv->task, PTRACE_MODE_READ); - if (!mm || IS_ERR(mm)) - return mm; + mm = priv->mm; + if (!mm || !atomic_inc_not_zero(&mm->mm_users)) + return NULL; down_read(&mm->mmap_sem); tail_vma = get_gate_vma(mm); @@ -240,9 +240,28 @@ static int proc_maps_open(struct inode *inode, struct file *file, return -ENOMEM; priv->pid = proc_pid(inode); + priv->mm = proc_mem_open(inode, PTRACE_MODE_READ); + if (IS_ERR(priv->mm)) { + int err = PTR_ERR(priv->mm); + + seq_release_private(inode, file); + return err; + } + return 0; } +static int proc_map_release(struct inode *inode, struct file *file) +{ + struct seq_file *seq = file->private_data; + struct proc_maps_private *priv = seq->private; + + if (priv->mm) + mmdrop(priv->mm); + + return seq_release_private(inode, file); +} + static int do_maps_open(struct inode *inode, struct file *file, const struct seq_operations *ops) { @@ -398,14 +417,14 @@ const struct file_operations proc_pid_maps_operations = { .open = pid_maps_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release_private, + .release = proc_map_release, }; const struct file_operations proc_tid_maps_operations = { .open = tid_maps_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release_private, + .release = proc_map_release, }; /* @@ -680,14 +699,14 @@ const struct file_operations proc_pid_smaps_operations = { .open = pid_smaps_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release_private, + .release = proc_map_release, }; const struct file_operations proc_tid_smaps_operations = { .open = tid_smaps_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release_private, + .release = proc_map_release, }; /* @@ -1544,13 +1563,13 @@ const struct file_operations proc_pid_numa_maps_operations = { .open = pid_numa_maps_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release_private, + .release = proc_map_release, }; const struct file_operations proc_tid_numa_maps_operations = { .open = tid_numa_maps_open, .read = seq_read, .llseek = seq_lseek, - .release = seq_release_private, + .release = proc_map_release, }; #endif /* CONFIG_NUMA */ -- cgit v1.2.3