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Re: [Qemu-devel] [PATCH V4 04/13] hw/9pfs: File system helper process fo
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH V4 04/13] hw/9pfs: File system helper process for qemu 9p proxy FS |
Date: |
Thu, 8 Dec 2011 18:31:14 +0000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Dec 05, 2011 at 09:48:41PM +0530, M. Mohan Kumar wrote:
> +static int read_request(int sockfd, struct iovec *iovec, ProxyHeader *header)
> +{
> + int retval;
> +
> + /*
> + * read the request header.
> + */
> + iovec->iov_len = 0;
> + retval = socket_read(sockfd, iovec->iov_base, PROXY_HDR_SZ);
> + if (retval < 0) {
> + return retval;
> + }
> + iovec->iov_len = PROXY_HDR_SZ;
> + retval = proxy_unmarshal(iovec, 0, "dd", &header->type, &header->size);
> + if (retval < 0) {
> + return retval;
> + }
> + /*
> + * We can't process message.size > PROXY_MAX_IO_SZ, read the complete
> + * message from the socket and ignore it. This ensures that
> + * we can correctly handle the next request. We also return
> + * ENOBUFS as error to indicate we ran out of buffer space.
> + */
> + if (header->size > PROXY_MAX_IO_SZ) {
> + int count, size;
> + size = header->size;
> + while (size > 0) {
> + count = MIN(PROXY_MAX_IO_SZ, size);
> + count = socket_read(sockfd, iovec->iov_base + PROXY_HDR_SZ,
> count);
> + if (count < 0) {
> + return count;
> + }
> + size -= count;
> + }
I'm not sure recovery attempts are worthwhile here. The client is
buggy, perhaps just refuse further work.
> + return -ENOBUFS;
> + }
header->size is (signed) int and we didn't check for header->size < 0.
Please use an unsigned type.
> + if (chroot(rpath) < 0) {
> + do_perror("chroot");
> + goto error;
> + }
> + umask(0);
We haven't changed into the chroot yet, we need chdir("/"). Otherwise
the current working directory is outside the chroot (and allows trivial
escape).
[Qemu-devel] [PATCH V4 05/13] hw/9pfs: Open and create files, M. Mohan Kumar, 2011/12/05
[Qemu-devel] [PATCH V4 06/13] hw/9pfs: Create other filesystem objects, M. Mohan Kumar, 2011/12/05
[Qemu-devel] [PATCH V4 07/13] hw/9pfs: Add stat/readlink/statfs for proxy FS, M. Mohan Kumar, 2011/12/05
[Qemu-devel] [PATCH V4 08/13] hw/9pfs: File ownership and others, M. Mohan Kumar, 2011/12/05
[Qemu-devel] [PATCH V4 09/13] hw/9pfs: xattr interfaces in proxy filesystem driver, M. Mohan Kumar, 2011/12/05
[Qemu-devel] [PATCH V4 10/13] hw/9pfs: Proxy getversion, M. Mohan Kumar, 2011/12/05