The patch titled
vfs: allow file truncations when both suid and write permissions set
has been added to the -mm tree. Its filename is
vfs-allow-file-truncations-when-both-suid-and-write-permissions-set.patch
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------------------------------------------------------
Subject: vfs: allow file truncations when both suid and write permissions set
From: Amerigo Wang <amwang@xxxxxxxxxx>
When suid is set and the non-owner user has write permission, any writing
into this file should be allowed and suid should be removed after that.
However, current kernel only allows writing without truncations, when we
do truncations on that file, we get EPERM. This is a bug.
Steps to reproduce this bug:
% ls -l rootdir/file1
-rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1
% echo h > rootdir/file1
zsh: operation not permitted: rootdir/file1
% ls -l rootdir/file1
-rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1
% echo h >> rootdir/file1
% ls -l rootdir/file1
-rwxrwxrwx 1 root root 5 Jun 25 16:34 rootdir/file1
Signed-off-by: WANG Cong <amwang@xxxxxxxxxx>
Cc: Eric Sandeen <esandeen@xxxxxxxxxx>
Cc: Eric Paris <eparis@xxxxxxxxxx>
Cc: Eugene Teo <eteo@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/open.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff -puN fs/open.c~vfs-allow-file-truncations-when-both-suid-and-write-permissions-set fs/open.c
--- a/fs/open.c~vfs-allow-file-truncations-when-both-suid-and-write-permissions-set
+++ a/fs/open.c
@@ -199,7 +199,7 @@ out:
int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
struct file *filp)
{
- int err;
+ int ret;
struct iattr newattrs;
/* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
@@ -214,12 +214,14 @@ int do_truncate(struct dentry *dentry, l
}
/* Remove suid/sgid on truncate too */
- newattrs.ia_valid |= should_remove_suid(dentry);
+ ret = should_remove_suid(dentry);
+ if (ret)
+ newattrs.ia_valid |= ret | ATTR_FORCE;
mutex_lock(&dentry->d_inode->i_mutex);
- err = notify_change(dentry, &newattrs);
+ ret = notify_change(dentry, &newattrs);
mutex_unlock(&dentry->d_inode->i_mutex);
- return err;
+ return ret;
}
static long do_sys_truncate(const char __user *pathname, loff_t length)
_
Patches currently in -mm which might be from amwang@xxxxxxxxxx are
origin.patch
linux-next.patch
selinux-adjust-rules-for-attr_force.patch
vfs-allow-file-truncations-when-both-suid-and-write-permissions-set.patch
xtensa-use-generic-sys_pipe.patch
kcore-fix-proc-kcores-statst_size.patch
elf-clean-up-fill_note_info.patch
elf-clean-up-fill_note_info-fix.patch
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