From: Yulei Zhang <yuleixzhang@xxxxxxxxxxx>
It is required by ptrace_writedata and ptrace_readdata to access
dmem memory remotely. The typical user is gdb, after this patch,
gdb is able to read & write memory owned by the attached process
Signed-off-by: Xiao Guangrong <gloryxiao@xxxxxxxxxxx>
Signed-off-by: Yulei Zhang <yuleixzhang@xxxxxxxxxxx>
---
fs/dmemfs/inode.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)
diff --git a/fs/dmemfs/inode.c b/fs/dmemfs/inode.c
index 8b0516d98ee7..4dacbf7e6844 100644
--- a/fs/dmemfs/inode.c
+++ b/fs/dmemfs/inode.c
@@ -367,6 +367,51 @@ static void radix_put_entry(void)
rcu_read_unlock();
}
+static bool check_vma_access(struct vm_area_struct *vma, int write)
+{
+ vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
+
+ return !!(vm_flags & vma->vm_flags);
+}
+
+static int
+dmemfs_access_dmem(struct vm_area_struct *vma, unsigned long addr,
+ void *buf, int len, int write)
+{
+ struct inode *inode = file_inode(vma->vm_file);
+ struct super_block *sb = inode->i_sb;
+ void *entry, *maddr;
+ int offset, pgoff;
+
+ if (!check_vma_access(vma, write))
+ return -EACCES;
+
+ pgoff = linear_page_index(vma, addr);
+ if (pgoff > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
+ return -EFAULT;
+
+ entry = radix_get_create_entry(vma, addr, inode, pgoff);
+ if (IS_ERR(entry))
+ return PTR_ERR(entry);
+
+ offset = addr & (sb->s_blocksize - 1);
+ addr = dmem_entry_to_addr(inode, entry);
+
+ /*
+ * it is not beyond vma's region as the vma should be aligned
+ * to blocksize
+ */
+ len = min(len, (int)(sb->s_blocksize - offset));
+ maddr = __va(addr);
+ if (write)
+ memcpy(maddr + offset, buf, len);
+ else
+ memcpy(buf, maddr + offset, len);
+ radix_put_entry();
+
+ return len;
+}
+
static vm_fault_t dmemfs_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
@@ -403,6 +448,7 @@ static unsigned long dmemfs_pagesize(struct vm_area_struct *vma)
static const struct vm_operations_struct dmemfs_vm_ops = {
.fault = dmemfs_fault,
.pagesize = dmemfs_pagesize,
+ .access = dmemfs_access_dmem,
};
int dmemfs_file_mmap(struct file *file, struct vm_area_struct *vma)
--
2.28.0
