From: viro@parcelfarce.linux.theplanet.co.uk
bernhard_heibler@gmx.de has discovered that NFS is very slow when writing to
a file which has execute permissions. See
http://bugme.osdl.org/show_bug.cgi?id=1936
This patch fixes remove_suid() to not try to modify the inode mode on every
write to such a file.
---
25-akpm/mm/filemap.c | 30 ++++++++++++++++++++----------
1 files changed, 20 insertions(+), 10 deletions(-)
diff -puN mm/filemap.c~remove_suid-fix mm/filemap.c
--- 25/mm/filemap.c~remove_suid-fix Thu Jan 22 16:11:18 2004
+++ 25-akpm/mm/filemap.c Thu Jan 22 16:11:18 2004
@@ -1495,22 +1495,32 @@ repeat:
return page;
}
+/*
+ * The logic we want is
+ *
+ * if suid or (sgid and xgrp)
+ * remove privs
+ */
void remove_suid(struct dentry *dentry)
{
struct iattr newattrs;
- struct inode *inode = dentry->d_inode;
- unsigned int mode = inode->i_mode & (S_ISUID|S_ISGID|S_IXGRP);
-
- if (!(mode & S_IXGRP))
- mode &= S_ISUID;
+ mode_t mode = dentry->d_inode->i_mode;
- /* were any of the uid bits set? */
- if (mode && !capable(CAP_FSETID)) {
- newattrs.ia_valid = ATTR_KILL_SUID|ATTR_KILL_SGID|ATTR_FORCE;
- notify_change(dentry, &newattrs);
+ if (likely(!(mode & S_ISUID))) {
+ /* common case - neither suid nor sgid */
+ if (likely(!(mode & S_ISGID)))
+ return;
+ /* if it's not group-executable, leave sgid alone */
+ if (!(mode & S_IXGRP))
+ return;
}
+ /* we have suid or real sgid; are we allowed to keep them? */
+ if (capable(CAP_FSETID))
+ return;
+ /* OK, remove SUID */
+ newattrs.ia_valid = ATTR_KILL_SUID|ATTR_KILL_SGID|ATTR_FORCE;
+ notify_change(dentry, &newattrs);
}
-
EXPORT_SYMBOL(remove_suid);
/*
_