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net: socket: don't set sk_uid to garbage value in ->setattr()

PATCH Applied Eric Biggers 3 participants 4 messages Dec 30, 2016 – Jan 1, 2017

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Networking Network drivers VFS Sockets
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Eric Biggers

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#0 lore raw

PATCH 1/1 net: socket: don't set sk_uid to garbage value in ->setattr()

From: Eric Biggers <[email protected]>

->setattr() was recently implemented for socket files to sync the socket inode's uid to the new 'sk_uid' member of struct sock. It does this by copying over the ia_uid member of struct iattr. However, ia_uid is actually only valid when ATTR_UID is set in ia_valid, indicating that the uid is being changed, e.g. by chown. Other metadata operations such as chmod or utimes leave ia_uid uninitialized. Therefore, sk_uid could be set to a "garbage" value from the stack.

Fix this by only copying the uid over when ATTR_UID is set.

Fixes 86741ec25462 ("net: core: Add a UID field to struct sock.")
Signed-off-by Eric Biggers <[email protected]>
---
 net/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
net/socket.c +1 -1
index 8487bf136e5c..a8c2307590b8 100644
@@ -537,7 +537,7 @@ int sockfs_setattr(struct dentry *dentry, struct iattr *iattr)
 {
 	int err = simple_setattr(dentry, iattr);
 
-	if (!err) {
+	if (!err && (iattr->ia_valid & ATTR_UID)) {
 		struct socket *sock = SOCKET_I(d_inode(dentry));
 
 		sock->sk->sk_uid = iattr->ia_uid;
Signature · 1 line
2.11.0
maintainer
#1 lore raw

From: Eric Biggers <[email protected]>
Date: Fri, 30 Dec 2016 17:42:32 -0600

Quoted 10 lines

From: Eric Biggers <[email protected]>

->setattr() was recently implemented for socket files to sync the socket inode's uid to the new 'sk_uid' member of struct sock. It does this by copying over the ia_uid member of struct iattr. However, ia_uid is actually only valid when ATTR_UID is set in ia_valid, indicating that the uid is being changed, e.g. by chown. Other metadata operations such as chmod or utimes leave ia_uid uninitialized. Therefore, sk_uid could be set to a "garbage" value from the stack.

Quoted 4 lines

Fix this by only copying the uid over when ATTR_UID is set.

Fixes 86741ec25462 ("net: core: Add a UID field to struct sock.")
Signed-off-by Eric Biggers <[email protected]>

Lorenzo, please review.

Tested-by Acked-by on v1 1/1
#2 lore raw
In reply to Eric Biggers

net/socket.c int sockfs_setattr(struct dentry *dentry, struct iattr *iattr) · line 540

Quoted 8 lines · Eric Biggers

->setattr() was recently implemented for socket files to sync the socket inode's uid to the new 'sk_uid' member of struct sock. It does this by copying over the ia_uid member of struct iattr. However, ia_uid is actually only valid when ATTR_UID is set in ia_valid, indicating that the uid is being changed, e.g. by chown.
[...]

net/socket.c +1 -1
-       if (!err) {
+       if (!err && (iattr->ia_valid & ATTR_UID)) {

Oops. Thanks for fixing this. Unit tested in
https://android-review.googlesource.com/316594 .

Tested-by Lorenzo Colitti <[email protected]>
Acked-by Lorenzo Colitti <[email protected]>
maintainer Applied
#3 lore raw

From: Lorenzo Colitti <[email protected]>
Date: Sun, 1 Jan 2017 16:57:23 +0900

Quoted 10 lines · Eric Biggers

net/socket.c int sockfs_setattr(struct dentry *dentry, struct iattr *iattr) · line 540

Quoted 8 lines

->setattr() was recently implemented for socket files to sync the socket inode's uid to the new 'sk_uid' member of struct sock. It does this by copying over the ia_uid member of struct iattr. However, ia_uid is actually only valid when ATTR_UID is set in ia_valid, indicating that the uid is being changed, e.g. by chown.
[...]

net/socket.c +1 -1
-       if (!err) {
+       if (!err && (iattr->ia_valid & ATTR_UID)) {
Quoted 5 lines

Oops. Thanks for fixing this. Unit tested in
https://android-review.googlesource.com/316594 .

Tested-by Lorenzo Colitti <[email protected]>
Acked-by Lorenzo Colitti <[email protected]>

Applied, thanks everyone.