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attr: add in_group_or_capable()

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commit 11c2a8700cdcabf9b639b7204a1e38e2a0b6798e upstream.

[backported to 5.10.y, prior to idmapped mounts]

In setattr_{copy,prepare}() we need to perform the same permission
checks to determine whether we need to drop the setgid bit or not.
Instead of open-coding it twice add a simple helper the encapsulates the
logic. We will reuse this helpers to make dropping the setgid bit during
write operations more consistent in a follow up patch.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Amir Goldstein
2023-03-18 12:15:24 +02:00
committed by Greg Kroah-Hartman
parent 94ac142c19
commit 24378d6f74
3 changed files with 27 additions and 10 deletions
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11
fs/attr.c
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@@ -18,6 +18,8 @@
#include <linux/evm.h>
#include <linux/ima.h>
#include "internal.h"
static bool chown_ok(const struct inode *inode, kuid_t uid)
{
if (uid_eq(current_fsuid(), inode->i_uid) &&
@@ -90,9 +92,8 @@ int setattr_prepare(struct dentry *dentry, struct iattr *attr)
if (!inode_owner_or_capable(inode))
return -EPERM;
/* Also check the setgid bit! */
if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
inode->i_gid) &&
!capable_wrt_inode_uidgid(inode, CAP_FSETID))
if (!in_group_or_capable(inode, (ia_valid & ATTR_GID) ?
attr->ia_gid : inode->i_gid))
attr->ia_mode &= ~S_ISGID;
}
@@ -193,9 +194,7 @@ void setattr_copy(struct inode *inode, const struct iattr *attr)
inode->i_ctime = attr->ia_ctime;
if (ia_valid & ATTR_MODE) {
umode_t mode = attr->ia_mode;
if (!in_group_p(inode->i_gid) &&
!capable_wrt_inode_uidgid(inode, CAP_FSETID))
if (!in_group_or_capable(inode, inode->i_gid))
mode &= ~S_ISGID;
inode->i_mode = mode;
}