ovl: get_write_access() in truncate (03bea604) · Commits · 戴 / test

When truncating a file we should check write access on the underlying inode. And we should do so on the lower file as well (before copy-up) for consistency. Original patch and test case by Aihua Zhang. - - >o >o - - test.c - - >o >o - - #include <stdio.h> #include <errno.h> #include <unistd.h> int main(int argc, char *argv[]) { int ret; ret = truncate(argv[0], 4096); if (ret != -1) { fprintf(stderr, "truncate(argv[0]) should have failed\n"); return 1; } if (errno != ETXTBSY) { perror("truncate(argv[0])"); return 1; } return 0; } - - >o >o - - >o >o - - >o >o - - Reported-by:

Aihua Zhang <zhangaihua1@huawei.com> Signed-off-by:

Miklos Szeredi <mszeredi@redhat.com> Cc: <stable@vger.kernel.org>

fs/overlayfs/inode.c

+21 −0

Original line number	Diff line number	Diff line
		@@ -59,16 +59,37 @@ int ovl_setattr(struct dentry dentry, struct iattr attr)
		if (err)
		goto out;

		if (attr->ia_valid & ATTR_SIZE) {
		struct inode *realinode = d_inode(ovl_dentry_real(dentry));

		err = -ETXTBSY;
		if (atomic_read(&realinode->i_writecount) < 0)
		goto out_drop_write;
		}

		err = ovl_copy_up(dentry);
		if (!err) {
		struct inode *winode = NULL;

		upperdentry = ovl_dentry_upper(dentry);

		if (attr->ia_valid & ATTR_SIZE) {
		winode = d_inode(upperdentry);
		err = get_write_access(winode);
		if (err)
		goto out_drop_write;
		}

		inode_lock(upperdentry->d_inode);
		err = notify_change(upperdentry, attr, NULL);
		if (!err)
		ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
		inode_unlock(upperdentry->d_inode);

		if (winode)
		put_write_access(winode);
		}
		out_drop_write:
		ovl_drop_write(dentry);
		out:
		return err;

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