sometimes HPUX nfs client sends a create request to linux nfs server(v2/v3).
the dump of the request is like:
obj_attributes
mode: value follows
set_it: value follows (1)
mode: 00
uid: no value
set_it: no value (0)
gid: value follows
set_it: value follows (1)
gid: 8030
size: value follows
set_it: value follows (1)
size: 0
atime: don't change
set_it: don't change (0)
mtime: don't change
set_it: don't change (0)
note that mode is 00(havs no rwx privilege even for the owner) and it requires
to set size to 0.
as current nfsd(v2/v3) implementation, the server does mainly 2 steps:
1) creates the file in mode specified by calling vfs_create().
2) sets attributes for the file by calling nfsd_setattr().
at step 2), it finally calls file system specific setattr() function which may
fails when checking permission because changing size needs WRITE privilege but
it has no since mode is 000.
for this case, a new file created, we may simply ignore the request of setting
size to 0. so that the WRITE privilege is not needed and finally success.
the patch is based on 2.6.27.10.
this is the 3rd edition of the patch. comparing with the 1st edition, it moves
common code and comment to function nfsd_check_ignore_resizing().
nfsd_create() and nfsd_create_v3() calls this function instead of embedding the
code and comment directly.
Signed-off-by: Wengang Wang <wen.gang.wang@xxxxxxxxxx>
--
vfs.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff -up ./fs/nfsd/vfs.c.orig ./fs/nfsd/vfs.c
--- ./fs/nfsd/vfs.c.orig 2009-02-10 09:59:07.000000000 +0800
+++ ./fs/nfsd/vfs.c 2009-02-10 10:07:31.000000000 +0800
@@ -1173,6 +1173,21 @@ nfsd_create_setattr(struct svc_rqst *rqs
return 0;
}
+/* HPUX client sometimes creates a file in mode 000, and sets size to 0.
+ * setting size to 0 may fail for some specific file systems by the permission
+ * checking which requires WRITE permission but the mode is 000.
+ * we ignore the resizing(to 0) on the just new created file, since the size is
+ * 0 after file created.
+ *
+ * call this only after vfs_create() is called.
+ * */
+static void
+nfsd_check_ignore_resizing(struct iattr *iap)
+{
+ if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size == 0))
+ iap->ia_valid &= ~ATTR_SIZE;
+}
+
/*
* Create a file (regular, directory, device, fifo); UNIX sockets
* not yet implemented.
@@ -1268,6 +1283,8 @@ nfsd_create(struct svc_rqst *rqstp, stru
switch (type) {
case S_IFREG:
host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
+ if (!host_err)
+ nfsd_check_ignore_resizing(iap);
break;
case S_IFDIR:
host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
@@ -1421,6 +1438,8 @@ nfsd_create_v3(struct svc_rqst *rqstp, s
/* setattr will sync the child (or not) */
}
+ nfsd_check_ignore_resizing(iap);
+
if (createmode == NFS3_CREATE_EXCLUSIVE) {
/* Cram the verifier into atime/mtime */
iap->ia_valid = ATTR_MTIME|ATTR_ATIME
--
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