From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/fs/attr.c | 126 ++++++++++++++++++++++++++++++++---------
1 files changed, 97 insertions(+), 29 deletions(-)
diff --git a/kernel/fs/attr.c b/kernel/fs/attr.c
index bea2f7c..375692e 100644
--- a/kernel/fs/attr.c
+++ b/kernel/fs/attr.c
@@ -18,6 +18,65 @@
#include <linux/evm.h>
#include <linux/ima.h>
+#include "internal.h"
+
+/**
+ * setattr_should_drop_sgid - determine whether the setgid bit needs to be
+ * removed
+ * @inode: inode to check
+ *
+ * This function determines whether the setgid bit needs to be removed.
+ * We retain backwards compatibility and require setgid bit to be removed
+ * unconditionally if S_IXGRP is set. Otherwise we have the exact same
+ * requirements as setattr_prepare() and setattr_copy().
+ *
+ * Return: ATTR_KILL_SGID if setgid bit needs to be removed, 0 otherwise.
+ */
+int setattr_should_drop_sgid(const struct inode *inode)
+{
+ umode_t mode = inode->i_mode;
+
+ if (!(mode & S_ISGID))
+ return 0;
+ if (mode & S_IXGRP)
+ return ATTR_KILL_SGID;
+ if (!in_group_or_capable(inode, inode->i_gid))
+ return ATTR_KILL_SGID;
+ return 0;
+}
+
+/**
+ * setattr_should_drop_suidgid - determine whether the set{g,u}id bit needs to
+ * be dropped
+ * @inode: inode to check
+ *
+ * This function determines whether the set{g,u}id bits need to be removed.
+ * If the setuid bit needs to be removed ATTR_KILL_SUID is returned. If the
+ * setgid bit needs to be removed ATTR_KILL_SGID is returned. If both
+ * set{g,u}id bits need to be removed the corresponding mask of both flags is
+ * returned.
+ *
+ * Return: A mask of ATTR_KILL_S{G,U}ID indicating which - if any - setid bits
+ * to remove, 0 otherwise.
+ */
+int setattr_should_drop_suidgid(struct inode *inode)
+{
+ umode_t mode = inode->i_mode;
+ int kill = 0;
+
+ /* suid always must be killed */
+ if (unlikely(mode & S_ISUID))
+ kill = ATTR_KILL_SUID;
+
+ kill |= setattr_should_drop_sgid(inode);
+
+ if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
+ return kill;
+
+ return 0;
+}
+EXPORT_SYMBOL(setattr_should_drop_suidgid);
+
static bool chown_ok(const struct inode *inode, kuid_t uid)
{
if (uid_eq(current_fsuid(), inode->i_uid) &&
@@ -90,9 +149,8 @@
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;
}
@@ -114,7 +172,7 @@
return 0;
}
-EXPORT_SYMBOL(setattr_prepare);
+EXPORT_SYMBOL_NS(setattr_prepare, ANDROID_GKI_VFS_EXPORT_ONLY);
/**
* inode_newsize_ok - may this inode be truncated to a given size
@@ -134,6 +192,8 @@
*/
int inode_newsize_ok(const struct inode *inode, loff_t offset)
{
+ if (offset < 0)
+ return -EINVAL;
if (inode->i_size < offset) {
unsigned long limit;
@@ -158,7 +218,7 @@
out_big:
return -EFBIG;
}
-EXPORT_SYMBOL(inode_newsize_ok);
+EXPORT_SYMBOL_NS(inode_newsize_ok, ANDROID_GKI_VFS_EXPORT_ONLY);
/**
* setattr_copy - copy simple metadata updates into the generic inode
@@ -184,19 +244,14 @@
if (ia_valid & ATTR_GID)
inode->i_gid = attr->ia_gid;
if (ia_valid & ATTR_ATIME)
- inode->i_atime = timespec64_trunc(attr->ia_atime,
- inode->i_sb->s_time_gran);
+ inode->i_atime = attr->ia_atime;
if (ia_valid & ATTR_MTIME)
- inode->i_mtime = timespec64_trunc(attr->ia_mtime,
- inode->i_sb->s_time_gran);
+ inode->i_mtime = attr->ia_mtime;
if (ia_valid & ATTR_CTIME)
- inode->i_ctime = timespec64_trunc(attr->ia_ctime,
- inode->i_sb->s_time_gran);
+ 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;
}
@@ -223,7 +278,7 @@
* the file open for write, as there can be no conflicting delegation in
* that case.
*/
-int notify_change2(struct vfsmount *mnt, struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
+int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
{
struct inode *inode = dentry->d_inode;
umode_t mode = inode->i_mode;
@@ -247,16 +302,32 @@
return -EPERM;
if (!inode_owner_or_capable(inode)) {
- error = inode_permission2(mnt, inode, MAY_WRITE);
+ error = inode_permission(inode, MAY_WRITE);
if (error)
return error;
}
}
if ((ia_valid & ATTR_MODE)) {
- umode_t amode = attr->ia_mode;
+ /*
+ * Don't allow changing the mode of symlinks:
+ *
+ * (1) The vfs doesn't take the mode of symlinks into account
+ * during permission checking.
+ * (2) This has never worked correctly. Most major filesystems
+ * did return EOPNOTSUPP due to interactions with POSIX ACLs
+ * but did still updated the mode of the symlink.
+ * This inconsistency led system call wrapper providers such
+ * as libc to block changing the mode of symlinks with
+ * EOPNOTSUPP already.
+ * (3) To even do this in the first place one would have to use
+ * specific file descriptors and quite some effort.
+ */
+ if (S_ISLNK(inode->i_mode))
+ return -EOPNOTSUPP;
+
/* Flag setting protected by i_mutex */
- if (is_sxid(amode))
+ if (is_sxid(attr->ia_mode))
inode->i_flags &= ~S_NOSEC;
}
@@ -265,8 +336,13 @@
attr->ia_ctime = now;
if (!(ia_valid & ATTR_ATIME_SET))
attr->ia_atime = now;
+ else
+ attr->ia_atime = timestamp_truncate(attr->ia_atime, inode);
if (!(ia_valid & ATTR_MTIME_SET))
attr->ia_mtime = now;
+ else
+ attr->ia_mtime = timestamp_truncate(attr->ia_mtime, inode);
+
if (ia_valid & ATTR_KILL_PRIV) {
error = security_inode_need_killpriv(dentry);
if (error < 0)
@@ -293,7 +369,7 @@
}
}
if (ia_valid & ATTR_KILL_SGID) {
- if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
+ if (mode & S_ISGID) {
if (!(ia_valid & ATTR_MODE)) {
ia_valid = attr->ia_valid |= ATTR_MODE;
attr->ia_mode = inode->i_mode;
@@ -330,9 +406,7 @@
if (error)
return error;
- if (mnt && inode->i_op->setattr2)
- error = inode->i_op->setattr2(mnt, dentry, attr);
- else if (inode->i_op->setattr)
+ if (inode->i_op->setattr)
error = inode->i_op->setattr(dentry, attr);
else
error = simple_setattr(dentry, attr);
@@ -345,10 +419,4 @@
return error;
}
-EXPORT_SYMBOL(notify_change2);
-
-int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
-{
- return notify_change2(NULL, dentry, attr, delegated_inode);
-}
-EXPORT_SYMBOL(notify_change);
+EXPORT_SYMBOL_NS(notify_change, ANDROID_GKI_VFS_EXPORT_ONLY);
--
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