by Felix von Leitne » Wed, 07 Mar 2001 04:10:04
If the owner or group is specified as -1, then that ID is not
changed.
If user !root says chown("/usr",-1,-1), he gets EPERM. Why?
He explicitly told the kernel that he does not actually want to change
anything. Why would the kernel say EPERM?
Felix
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by Andries.Brou.. » Wed, 07 Mar 2001 05:10:04
If user !root says chown("/usr",-1,-1), he gets EPERM. Why?
Because the standard says:
The chown( ) function shall fail if:
[EPERM] The effective user ID does not match the owner of the file, or ..
Andries
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I've just noticed that I can't cown my own files to other users under
Linux. Tried it under RedHat 5.2 and Slackware 3.5
Examining kernel sources I found in fs/inode.c, line 307 (function
inode_change_ok):
/*make sure a caller can chown*/
if ((attr->ia_valid & ATTR_UID) &&
(current->fsusid != inode->i_uid ||
attr->ia_uid != inode->i_uid) && !fsuser())
return -EPERM;
If my brain is still worth any thing, this means
"if you are trying to change UID and you are not currently owner of
inode ?OR? you are trying to change UID to something other then it
currently is, and you are not SU, then .....",
that is if you are trying to change owner user and you are not SU, you
are automatically denied access.
I thought it had to be
/*make sure a caller can chown*/
if ((attr->ia_valid & ATTR_UID) && attr->ia_uid != inode->i_uid &&
(current->fsusid != inode->i_uid || !fsuser())
return -EPERM;
"if you are trying to change UID to something other then it is now and
you are not owner of inode or SU, then deny access"
Is it a feature of linux,
or perhaps my understanding of meaning of structures is wrong?
inode -- inode we want to change
attr -- new attributes
current->fsuser -- UID of caller
if I am wrong about that, please correct me.
Thanks.
Ilya.
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