Separate the handling of the local ia_valid bitmask from the one in
attr->ia_valid. This allows us to hand off the actual handling of the
ATTR_KILL_* flags to the .setattr i_op when one is defined.
notify_change still needs to process those flags for the local ia_valid
variable, since it uses that to decide whether to return early, and to pass
a (hopefully) appropriate bitmask to fsnotify_change.
Also, check the ia_valid after the setattr op returns and see if either
ATTR_KILL_* bit is set. If so, then throw a warning and try to clear the
bits in the "standard" way. This should help us to catch filesystems that
don't handle these bits correctly without breaking them outright.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/attr.c | 91 ++++++++++++++++++++++++++++++++++++++++-----------
include/linux/fs.h | 1 +
2 files changed, 72 insertions(+), 20 deletions(-)
diff --git a/fs/attr.c b/fs/attr.c
index ae58bd3..50c8ce4 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -100,15 +100,53 @@ int inode_setattr(struct inode * inode, struct iattr * attr)
}
EXPORT_SYMBOL(inode_setattr);
+/**
+ * generic_attrkill - helper to convert ATTR_KILL_* bits into mode change
+ * @mode: current mode of inode
+ * @attr: inode attribute changes requested by VFS
+ * Context: anywhere
+ *
+ * This is a helper function to convert ATTR_KILL_SUID and ATTR_KILL_SGID
+ * into a mode change. Filesystems should call this from their setattr
+ * inode op when they want "conventional" setuid-clearing behavior.
+ *
+ * Filesystems that declare a setattr inode operation are now expected to
+ * handle the ATTR_KILL_SUID and ATTR_KILL_SGID bits appropriately. The VFS
+ * no longer automatically converts these bits to a mode change for
+ * inodes that have their own setattr operation.
+ **/
+void generic_attrkill(mode_t mode, struct iattr *attr)
+{
+ if (attr->ia_valid & ATTR_KILL_SUID) {
+ attr->ia_valid &= ~ATTR_KILL_SUID;
+ if (mode & S_ISUID) {
+ if (!(attr->ia_valid & ATTR_MODE)) {
+ attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode = mode;
+ }
+ attr->ia_mode &= ~S_ISUID;
+ }
+ }
+ if (attr->ia_valid & ATTR_KILL_SGID) {
+ attr->ia_valid &= ~ATTR_KILL_SGID;
+ if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
+ if (!(attr->ia_valid & ATTR_MODE)) {
+ attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode = mode;
+ }
+ attr->ia_mode &= ~S_ISGID;
+ }
+ }
+}
+EXPORT_SYMBOL(generic_attrkill);
+
int notify_change(struct dentry * dentry, struct iattr * attr)
{
struct inode *inode = dentry->d_inode;
- mode_t mode;
- int error;
+ int error, once = 0;
struct timespec now;
unsigned int ia_valid = attr->ia_valid;
- mode = inode->i_mode;
now = current_fs_time(inode->i_sb);
attr->ia_ctime = now;
@@ -126,36 +164,49 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
return error;
}
if (ia_valid & ATTR_KILL_SUID) {
- attr->ia_valid &= ~ATTR_KILL_SUID;
- if (mode & S_ISUID) {
- if (!(ia_valid & ATTR_MODE)) {
- ia_valid = attr->ia_valid |= ATTR_MODE;
- attr->ia_mode = inode->i_mode;
- }
- attr->ia_mode &= ~S_ISUID;
- }
+ ia_valid &= ~ATTR_KILL_SUID;
+ if (inode->i_mode & S_ISUID)
+ ia_valid |= ATTR_MODE;
}
if (ia_valid & ATTR_KILL_SGID) {
- attr->ia_valid &= ~ ATTR_KILL_SGID;
- if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
- if (!(ia_valid & ATTR_MODE)) {
- ia_valid = attr->ia_valid |= ATTR_MODE;
- attr->ia_mode = inode->i_mode;
- }
- attr->ia_mode &= ~S_ISGID;
- }
+ ia_valid &= ~ATTR_KILL_SGID;
+ if ((inode->i_mode & (S_ISGID | S_IXGRP)) ==
+ (S_ISGID | S_IXGRP))
+ ia_valid |= ATTR_MODE;
}
- if (!attr->ia_valid)
+ if (!ia_valid)
return 0;
if (ia_valid & ATTR_SIZE)
down_write(&dentry->d_inode->i_alloc_sem);
if (inode->i_op && inode->i_op->setattr) {
+retry:
error = security_inode_setattr(dentry, attr);
if (!error)
error = inode->i_op->setattr(dentry, attr);
+ /*
+ * if ATTR_KILL_SUID or ATTR_KILL_SGID is still set, then
+ * assume that the setattr inode op didn't handle them
+ * correctly. Try to clear these bits the standard way
+ * with a second setattr call and printk a warning.
+ */
+ if (!error && !once && unlikely(attr->ia_valid &
+ (ATTR_KILL_SUID|ATTR_KILL_SGID))) {
+ attr->ia_valid &=
+ (ATTR_FORCE|ATTR_KILL_SUID|ATTR_KILL_SGID);
+ generic_attrkill(inode->i_mode, attr);
+ ++once;
+ if (printk_ratelimit())
+ printk(KERN_ERR "%s: %s doesn't seem to "
+ "handle setuid/setgid bit killing "
+ "correctly. Report this to filesystem "
+ "maintainer.\n", __func__,
+ inode->i_sb->s_type->name);
+ goto retry;
+ }
} else {
+ generic_attrkill(inode->i_mode, attr);
error = inode_change_ok(inode, attr);
if (!error)
error = security_inode_setattr(dentry, attr);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 30eb32f..6ba6830 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1679,6 +1679,7 @@ extern int do_remount_sb(struct super_block *sb, int flags,
#ifdef CONFIG_BLOCK
extern sector_t bmap(struct inode *, sector_t);
#endif
+extern void generic_attrkill(mode_t mode, struct iattr *attr);
extern int notify_change(struct dentry *, struct iattr *);
extern int permission(struct inode *, int, struct nameidata *);
extern int generic_permission(struct inode *, int,
--
1.5.2.2
-
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