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vfs: forbid write access when reading a file into memory

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This patch is based on top of the "vfs: support for a common kernel file
loader" patch set.  In general when the kernel is reading a file into
memory it does not want anything else writing to it.

The kernel currently only forbids write access to a file being executed.
This patch extends this locking to files being read by the kernel.

Changelog:
- moved function to kernel_read_file() - Mimi
- updated patch description - Mimi

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@huawei.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Reviewed-by: Luis R. Rodriguez <mcgrof@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Dmitry Kasatkin 2014-10-26 12:42:07 +02:00 committed by Mimi Zohar
parent da20dfe6b5
commit 39d637af5a
1 changed files with 21 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

29
fs/exec.c
View file

@ -850,15 +850,25 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
if (ret) if (ret)
return ret; return ret;
ret = deny_write_access(file);
if (ret)
return ret;
i_size = i_size_read(file_inode(file)); i_size = i_size_read(file_inode(file));
if (max_size > 0 && i_size > max_size) if (max_size > 0 && i_size > max_size) {
return -EFBIG; ret = -EFBIG;
if (i_size <= 0) goto out;
return -EINVAL; }
if (i_size <= 0) {
ret = -EINVAL;
goto out;
}
*buf = vmalloc(i_size); *buf = vmalloc(i_size);
if (!*buf) if (!*buf) {
return -ENOMEM; ret = -ENOMEM;
goto out;
}
pos = 0; pos = 0;
while (pos < i_size) { while (pos < i_size) {
@ -876,18 +886,21 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
if (pos != i_size) { if (pos != i_size) {
ret = -EIO; ret = -EIO;
goto out; goto out_free;
} }
ret = security_kernel_post_read_file(file, *buf, i_size, id); ret = security_kernel_post_read_file(file, *buf, i_size, id);
if (!ret) if (!ret)
*size = pos; *size = pos;
out: out_free:
if (ret < 0) { if (ret < 0) {
vfree(*buf); vfree(*buf);
*buf = NULL; *buf = NULL;
} }
out:
allow_write_access(file);
return ret; return ret;
} }
EXPORT_SYMBOL_GPL(kernel_read_file); EXPORT_SYMBOL_GPL(kernel_read_file);