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link_path_walk(): sample parent's i_uid and i_mode for the last component

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-03-05 11:34:48 -05:00
parent 60ef60c7d7
commit 0f70595301
1 changed files with 7 additions and 10 deletions
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17
fs/namei.c
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@ -505,6 +505,8 @@ struct nameidata {
struct nameidata *saved;
unsigned root_seq;
int dfd;
kuid_t dir_uid;
umode_t dir_mode;
} __randomize_layout;
static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
@ -938,9 +940,6 @@ int sysctl_protected_regular __read_mostly;
*/
static inline int may_follow_link(struct nameidata *nd, const struct inode *inode)
{
const struct inode *parent;
kuid_t puid;
if (!sysctl_protected_symlinks)
return 0;
@ -949,13 +948,11 @@ static inline int may_follow_link(struct nameidata *nd, const struct inode *inod
return 0;
/* Allowed if parent directory not sticky and world-writable. */
parent = nd->inode;
if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
return 0;
/* Allowed if parent directory and link owner match. */
puid = parent->i_uid;
if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
if (uid_valid(nd->dir_uid) && uid_eq(nd->dir_uid, inode->i_uid))
return 0;
if (nd->flags & LOOKUP_RCU)
@ -2159,6 +2156,8 @@ static int link_path_walk(const char *name, struct nameidata *nd)
OK:
/* pathname or trailing symlink, done */
if (!depth) {
nd->dir_uid = nd->inode->i_uid;
nd->dir_mode = nd->inode->i_mode;
nd->flags &= ~LOOKUP_PARENT;
return 0;
}
@ -3224,8 +3223,6 @@ static const char *open_last_lookups(struct nameidata *nd,
static const char *do_last(struct nameidata *nd,
struct file *file, const struct open_flags *op)
{
kuid_t dir_uid = nd->inode->i_uid;
umode_t dir_mode = nd->inode->i_mode;
int open_flag = op->open_flag;
bool do_truncate;
int acc_mode;
@ -3241,7 +3238,7 @@ static const char *do_last(struct nameidata *nd,
if (open_flag & O_CREAT) {
if (d_is_dir(nd->path.dentry))
return ERR_PTR(-EISDIR);
error = may_create_in_sticky(dir_mode, dir_uid,
error = may_create_in_sticky(nd->dir_mode, nd->dir_uid,
d_backing_inode(nd->path.dentry));
if (unlikely(error))
return ERR_PTR(error);