This looks good from our side - thanks! Reviewed-by: mwilliamson@xxxxxxxxxxxxxxxxx Tested-by: mwilliamson@xxxxxxxxxxxxxxxxx On Tue, Jun 9, 2015 at 9:00 PM, Konstantin Khlebnikov <koct9i@xxxxxxxxx> wrote: > From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > > This patch moves permission checks from pagemap_read() into pagemap_open(). > > Pointer to mm is saved in file->private_data. This reference pins only > mm_struct itself. /proc/*/mem, maps, smaps already work in the same way. > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > Link: http://lkml.kernel.org/r/CA+55aFyKpWrt_Ajzh1rzp_GcwZ4=6Y=kOv8hBz172CFJp6L8Tg@xxxxxxxxxxxxxx > --- > fs/proc/task_mmu.c | 48 ++++++++++++++++++++++++++++-------------------- > 1 file changed, 28 insertions(+), 20 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 6dee68d..21bc251 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1227,40 +1227,33 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask, > static ssize_t pagemap_read(struct file *file, char __user *buf, > size_t count, loff_t *ppos) > { > - struct task_struct *task = get_proc_task(file_inode(file)); > - struct mm_struct *mm; > + struct mm_struct *mm = file->private_data; > struct pagemapread pm; > - int ret = -ESRCH; > struct mm_walk pagemap_walk = {}; > unsigned long src; > unsigned long svpfn; > unsigned long start_vaddr; > unsigned long end_vaddr; > - int copied = 0; > + int ret = 0, copied = 0; > > - if (!task) > + if (!mm || !atomic_inc_not_zero(&mm->mm_users)) > goto out; > > ret = -EINVAL; > /* file position must be aligned */ > if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES)) > - goto out_task; > + goto out_mm; > > ret = 0; > if (!count) > - goto out_task; > + goto out_mm; > > pm.v2 = soft_dirty_cleared; > pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT); > pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY); > ret = -ENOMEM; > if (!pm.buffer) > - goto out_task; > - > - mm = mm_access(task, PTRACE_MODE_READ); > - ret = PTR_ERR(mm); > - if (!mm || IS_ERR(mm)) > - goto out_free; > + goto out_mm; > > pagemap_walk.pmd_entry = pagemap_pte_range; > pagemap_walk.pte_hole = pagemap_pte_hole; > @@ -1273,10 +1266,10 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, > src = *ppos; > svpfn = src / PM_ENTRY_BYTES; > start_vaddr = svpfn << PAGE_SHIFT; > - end_vaddr = TASK_SIZE_OF(task); > + end_vaddr = mm->task_size; > > /* watch out for wraparound */ > - if (svpfn > TASK_SIZE_OF(task) >> PAGE_SHIFT) > + if (svpfn > mm->task_size >> PAGE_SHIFT) > start_vaddr = end_vaddr; > > /* > @@ -1303,7 +1296,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, > len = min(count, PM_ENTRY_BYTES * pm.pos); > if (copy_to_user(buf, pm.buffer, len)) { > ret = -EFAULT; > - goto out_mm; > + goto out_free; > } > copied += len; > buf += len; > @@ -1313,24 +1306,38 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, > if (!ret || ret == PM_END_OF_BUFFER) > ret = copied; > > -out_mm: > - mmput(mm); > out_free: > kfree(pm.buffer); > -out_task: > - put_task_struct(task); > +out_mm: > + mmput(mm); > out: > return ret; > } > > static int pagemap_open(struct inode *inode, struct file *file) > { > + struct mm_struct *mm; > + > /* do not disclose physical addresses: attack vector */ > if (!capable(CAP_SYS_ADMIN)) > return -EPERM; > pr_warn_once("Bits 55-60 of /proc/PID/pagemap entries are about " > "to stop being page-shift some time soon. See the " > "linux/Documentation/vm/pagemap.txt for details.\n"); > + > + mm = proc_mem_open(inode, PTRACE_MODE_READ); > + if (IS_ERR(mm)) > + return PTR_ERR(mm); > + file->private_data = mm; > + return 0; > +} > + > +static int pagemap_release(struct inode *inode, struct file *file) > +{ > + struct mm_struct *mm = file->private_data; > + > + if (mm) > + mmdrop(mm); > return 0; > } > > @@ -1338,6 +1345,7 @@ const struct file_operations proc_pagemap_operations = { > .llseek = mem_lseek, /* borrow this */ > .read = pagemap_read, > .open = pagemap_open, > + .release = pagemap_release, > }; > #endif /* CONFIG_PROC_PAGE_MONITOR */ > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>