Re: [Libguestfs] [nbdkit PATCH] connections: Improve error responses

We had several inconsistencies from the NBD spec when diagnosing bad client messages: - FLUSH is not generally forbidden on a read-only export (so failing with EPERM is wrong) [meanwhile, if we don't advertise flush because plugin_can_flush() fails, then rejecting with EINVAL is still okay] - returning EPERM (aka EROFS) for read-only exports should probably take precedence over anything else - out-of-bounds WRITE and WRITE_ZEROES should fail with ENOSPC, not EIO - out-of-bounds READ and TRIM should fail with EINVAL, not EIO We also had dead code: valid_range() and validate_request() cannot return -1. Make these functions return bool instead. And finally, fix a comment typo. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- src/connections.c | 53 ++++++++++++++++++++++++----------------------------- 1 file changed, 24 insertions(+), 29 deletions(-) diff --git a/src/connections.c b/src/connections.c index 8dc1925..264037d 100644 --- a/src/connections.c +++ b/src/connections.c @@ -666,7 +666,7 @@ negotiate_handshake (struct connection *conn) return r; } -static int +static bool valid_range (struct connection *conn, uint64_t offset, uint32_t count) { uint64_t exportsize = conn->exportsize; @@ -674,27 +674,34 @@ valid_range (struct connection *conn, uint64_t offset, uint32_t count) return count > 0 && offset <= exportsize && offset + count <= exportsize; } -static int +static bool validate_request (struct connection *conn, uint32_t cmd, uint32_t flags, uint64_t offset, uint32_t count, uint32_t *error) { int r; + /* Readonly connection? */ + if (conn->readonly && + (cmd == NBD_CMD_WRITE || + cmd == NBD_CMD_TRIM || cmd == NBD_CMD_WRITE_ZEROES)) { + nbdkit_error ("invalid request: write request on readonly connection"); + *error = EROFS; + return false; + } + /* Validate cmd, offset, count. */ switch (cmd) { case NBD_CMD_READ: case NBD_CMD_WRITE: case NBD_CMD_TRIM: case NBD_CMD_WRITE_ZEROES: - r = valid_range (conn, offset, count); - if (r == -1) - return -1; - if (r == 0) { + if (!valid_range (conn, offset, count)) { /* XXX Allow writes to extend the disk? */ nbdkit_error ("invalid request: offset and length are out of range"); - *error = EIO; - return 0; + *error = (cmd == NBD_CMD_WRITE || + cmd == NBD_CMD_WRITE_ZEROES) ? ENOSPC : EINVAL; + return false; } break; @@ -702,7 +709,7 @@ validate_request (struct connection *conn, if (offset != 0 || count != 0) { nbdkit_error ("invalid flush request: expecting offset and length == 0"); *error = EINVAL; - return 0; + return false; } break; @@ -710,20 +717,20 @@ validate_request (struct connection *conn, nbdkit_error ("invalid request: unknown command (%" PRIu32 ") ignored", cmd); *error = EINVAL; - return 0; + return false; } /* Validate flags */ if (flags & ~(NBD_CMD_FLAG_FUA | NBD_CMD_FLAG_NO_HOLE)) { nbdkit_error ("invalid request: unknown flag (0x%x)", flags); *error = EINVAL; - return 0; + return false; } if ((flags & NBD_CMD_FLAG_NO_HOLE) && cmd != NBD_CMD_WRITE_ZEROES) { nbdkit_error ("invalid request: NO_HOLE flag needs WRITE_ZEROES request"); *error = EINVAL; - return 0; + return false; } /* Refuse over-large read and write requests. */ @@ -732,33 +739,24 @@ validate_request (struct connection *conn, nbdkit_error ("invalid request: data request is too large (%" PRIu32 " > %d)", count, MAX_REQUEST_SIZE); *error = ENOMEM; - return 0; - } - - /* Readonly connection? */ - if (conn->readonly && - (cmd == NBD_CMD_WRITE || cmd == NBD_CMD_FLUSH || - cmd == NBD_CMD_TRIM || cmd == NBD_CMD_WRITE_ZEROES)) { - nbdkit_error ("invalid request: write request on readonly connection"); - *error = EROFS; - return 0; + return false; } /* Flush allowed? */ if (!conn->can_flush && cmd == NBD_CMD_FLUSH) { nbdkit_error ("invalid request: flush operation not supported"); *error = EINVAL; - return 0; + return false; } /* Trim allowed? */ if (!conn->can_trim && cmd == NBD_CMD_TRIM) { nbdkit_error ("invalid request: trim operation not supported"); *error = EINVAL; - return 0; + return false; } - return 1; /* Commands validates. */ + return true; /* Command validates. */ } /* Grab the appropriate error value. @@ -970,10 +968,7 @@ recv_request_send_reply (struct connection *conn) } /* Validate the request. */ - r = validate_request (conn, cmd, flags, offset, count, &error); - if (r == -1) - return -1; - if (r == 0) { /* request not valid */ + if (!validate_request (conn, cmd, flags, offset, count, &error)) { if (cmd == NBD_CMD_WRITE && skip_over_write_buffer (conn->sockin, count) < 0) return -1;