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symlink: handle_open() detects symlink creation

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added check in handle_open() to avoid calling CREATE/OPEN when we're creating a symlink:

if (args->disposition == FILE_CREATE &&
    args->access_mask == (FILE_WRITE_ATTRIBUTES | SYNCHRONIZE | DELETE) &&
    args->access_mode == 0 &&
    args->create_opts & FILE_OPEN_REPARSE_POINT)

these are the open arguments we get from the CreateSymbolicLink() syscall.  by avoiding the call to CREATE/OPEN on handle_open(), we save ourselves from having to REMOVE the file before creating the symlink

added a check to handle_symlink() in case the file was actually created on open (an application could open the file with different arguments, and send the FSCTL_SET_REPARSE_POINT manually), and removes the file first

Signed-off-by: Casey Bodley <cbodley@citi.umich.edu>
This commit is contained in:
Casey Bodley 2010-09-23 12:59:26 -04:00 • committed by unknown
parent 62fa6176be
commit ccdaa169eb
4 changed files with 42 additions and 6 deletions
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40
daemon/open.c
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@ -119,7 +119,7 @@ out:
return status;
}
static BOOLEAN do_lookup(uint32_t type, ULONG access_mask, ULONG disposition)
static BOOLEAN do_lookup(uint32_t type, ULONG access_mask, ULONG disposition)
{
if (type == NF4DIR) {
if (disposition == FILE_OPEN || disposition == FILE_OVERWRITE) {
@ -132,10 +132,10 @@ static BOOLEAN do_lookup(uint32_t type, ULONG access_mask, ULONG disposition)
}
if ((access_mask & FILE_READ_DATA) ||
(access_mask & FILE_WRITE_DATA) ||
(access_mask & FILE_APPEND_DATA) ||
(access_mask & FILE_EXECUTE))
return FALSE;
(access_mask & FILE_WRITE_DATA) ||
(access_mask & FILE_APPEND_DATA) ||
(access_mask & FILE_EXECUTE))
return FALSE;
else {
dprintf(1, "Open call that wants to manage attributes\n");
return TRUE;
@ -274,7 +274,35 @@ int handle_open(nfs41_upcall *upcall)
state->type = info.type;
} else if (status != ERROR_FILE_NOT_FOUND)
goto out_free_state;
if (do_lookup(state->type, args->access_mask, args->disposition)) {
/* XXX: this is a hard-coded check for the open arguments we see from
* the CreateSymbolicLink() system call. we respond to this by deferring
* the CREATE until we get the upcall to set the symlink. this approach
* is troublesome for two reasons:
* -an application might use these exact arguments to create a normal
* file, and we would return success without actually creating it
* -an application could create a symlink by sending the FSCTL to set
* the reparse point manually, and their open might be different. in
* this case we'd create the file on open, and need to remove it
* before creating the symlink */
if (args->disposition == FILE_CREATE &&
args->access_mask == (FILE_WRITE_ATTRIBUTES | SYNCHRONIZE | DELETE) &&
args->access_mode == 0 &&
args->create_opts & FILE_OPEN_REPARSE_POINT) {
/* fail if the file already exists */
uint32_t create;
status = map_disposition_2_nfsopen(args->disposition, status,
&create, &upcall->last_error);
if (status)
goto out_free_state;
/* defer the call to CREATE until we get the symlink set upcall */
dprintf(1, "trying to create a symlink, deferring create\n");
/* because of WRITE_ATTR access, be prepared for a setattr upcall;
* will crash if the superblock is null, so use the parent's */
state->file.fh.superblock = state->parent.fh.superblock;
} else if (do_lookup(state->type, args->access_mask, args->disposition)) {
if (status) {
dprintf(1, "nfs41_lookup failed with %d\n", status);
goto out_free_state;