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-rw-r--r--fs/namei.c222
1 files changed, 191 insertions, 31 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 208c6aa4a989..e615ff37e27d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -15,7 +15,7 @@
*/
#include <linux/init.h>
-#include <linux/module.h>
+#include <linux/export.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/namei.h>
@@ -161,7 +161,7 @@ static char *getname_flags(const char __user *filename, int flags, int *empty)
char *getname(const char __user * filename)
{
- return getname_flags(filename, 0, 0);
+ return getname_flags(filename, 0, NULL);
}
#ifdef CONFIG_AUDITSYSCALL
@@ -642,7 +642,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
cond_resched();
current->total_link_count++;
- touch_atime(link->mnt, dentry);
+ touch_atime(link);
nd_set_link(nd, NULL);
error = security_inode_follow_link(link->dentry, nd);
@@ -1095,8 +1095,10 @@ static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentr
struct dentry *old;
/* Don't create child dentry for a dead directory. */
- if (unlikely(IS_DEADDIR(inode)))
+ if (unlikely(IS_DEADDIR(inode))) {
+ dput(dentry);
return ERR_PTR(-ENOENT);
+ }
old = inode->i_op->lookup(inode, dentry, nd);
if (unlikely(old)) {
@@ -1373,6 +1375,157 @@ static inline int can_lookup(struct inode *inode)
}
/*
+ * We can do the critical dentry name comparison and hashing
+ * operations one word at a time, but we are limited to:
+ *
+ * - Architectures with fast unaligned word accesses. We could
+ * do a "get_unaligned()" if this helps and is sufficiently
+ * fast.
+ *
+ * - Little-endian machines (so that we can generate the mask
+ * of low bytes efficiently). Again, we *could* do a byte
+ * swapping load on big-endian architectures if that is not
+ * expensive enough to make the optimization worthless.
+ *
+ * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
+ * do not trap on the (extremely unlikely) case of a page
+ * crossing operation.
+ *
+ * - Furthermore, we need an efficient 64-bit compile for the
+ * 64-bit case in order to generate the "number of bytes in
+ * the final mask". Again, that could be replaced with a
+ * efficient population count instruction or similar.
+ */
+#ifdef CONFIG_DCACHE_WORD_ACCESS
+
+#ifdef CONFIG_64BIT
+
+/*
+ * Jan Achrenius on G+: microoptimized version of
+ * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
+ * that works for the bytemasks without having to
+ * mask them first.
+ */
+static inline long count_masked_bytes(unsigned long mask)
+{
+ return mask*0x0001020304050608ul >> 56;
+}
+
+static inline unsigned int fold_hash(unsigned long hash)
+{
+ hash += hash >> (8*sizeof(int));
+ return hash;
+}
+
+#else /* 32-bit case */
+
+/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
+static inline long count_masked_bytes(long mask)
+{
+ /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
+ long a = (0x0ff0001+mask) >> 23;
+ /* Fix the 1 for 00 case */
+ return a & mask;
+}
+
+#define fold_hash(x) (x)
+
+#endif
+
+unsigned int full_name_hash(const unsigned char *name, unsigned int len)
+{
+ unsigned long a, mask;
+ unsigned long hash = 0;
+
+ for (;;) {
+ a = *(unsigned long *)name;
+ if (len < sizeof(unsigned long))
+ break;
+ hash += a;
+ hash *= 9;
+ name += sizeof(unsigned long);
+ len -= sizeof(unsigned long);
+ if (!len)
+ goto done;
+ }
+ mask = ~(~0ul << len*8);
+ hash += mask & a;
+done:
+ return fold_hash(hash);
+}
+EXPORT_SYMBOL(full_name_hash);
+
+#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
+#define ONEBYTES REPEAT_BYTE(0x01)
+#define SLASHBYTES REPEAT_BYTE('/')
+#define HIGHBITS REPEAT_BYTE(0x80)
+
+/* Return the high bit set in the first byte that is a zero */
+static inline unsigned long has_zero(unsigned long a)
+{
+ return ((a - ONEBYTES) & ~a) & HIGHBITS;
+}
+
+/*
+ * Calculate the length and hash of the path component, and
+ * return the length of the component;
+ */
+static inline unsigned long hash_name(const char *name, unsigned int *hashp)
+{
+ unsigned long a, mask, hash, len;
+
+ hash = a = 0;
+ len = -sizeof(unsigned long);
+ do {
+ hash = (hash + a) * 9;
+ len += sizeof(unsigned long);
+ a = *(unsigned long *)(name+len);
+ /* Do we have any NUL or '/' bytes in this word? */
+ mask = has_zero(a) | has_zero(a ^ SLASHBYTES);
+ } while (!mask);
+
+ /* The mask *below* the first high bit set */
+ mask = (mask - 1) & ~mask;
+ mask >>= 7;
+ hash += a & mask;
+ *hashp = fold_hash(hash);
+
+ return len + count_masked_bytes(mask);
+}
+
+#else
+
+unsigned int full_name_hash(const unsigned char *name, unsigned int len)
+{
+ unsigned long hash = init_name_hash();
+ while (len--)
+ hash = partial_name_hash(*name++, hash);
+ return end_name_hash(hash);
+}
+EXPORT_SYMBOL(full_name_hash);
+
+/*
+ * We know there's a real path component here of at least
+ * one character.
+ */
+static inline unsigned long hash_name(const char *name, unsigned int *hashp)
+{
+ unsigned long hash = init_name_hash();
+ unsigned long len = 0, c;
+
+ c = (unsigned char)*name;
+ do {
+ len++;
+ hash = partial_name_hash(c, hash);
+ c = (unsigned char)name[len];
+ } while (c && c != '/');
+ *hashp = end_name_hash(hash);
+ return len;
+}
+
+#endif
+
+/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
* the final dentry. We expect 'base' to be positive and a directory.
@@ -1392,31 +1545,22 @@ static int link_path_walk(const char *name, struct nameidata *nd)
/* At this point we know we have a real path component. */
for(;;) {
- unsigned long hash;
struct qstr this;
- unsigned int c;
+ long len;
int type;
err = may_lookup(nd);
if (err)
break;
+ len = hash_name(name, &this.hash);
this.name = name;
- c = *(const unsigned char *)name;
-
- hash = init_name_hash();
- do {
- name++;
- hash = partial_name_hash(c, hash);
- c = *(const unsigned char *)name;
- } while (c && (c != '/'));
- this.len = name - (const char *) this.name;
- this.hash = end_name_hash(hash);
+ this.len = len;
type = LAST_NORM;
- if (this.name[0] == '.') switch (this.len) {
+ if (name[0] == '.') switch (len) {
case 2:
- if (this.name[1] == '.') {
+ if (name[1] == '.') {
type = LAST_DOTDOT;
nd->flags |= LOOKUP_JUMPED;
}
@@ -1435,12 +1579,18 @@ static int link_path_walk(const char *name, struct nameidata *nd)
}
}
- /* remove trailing slashes? */
- if (!c)
+ if (!name[len])
goto last_component;
- while (*++name == '/');
- if (!*name)
+ /*
+ * If it wasn't NUL, we know it was '/'. Skip that
+ * slash, and continue until no more slashes.
+ */
+ do {
+ len++;
+ } while (unlikely(name[len] == '/'));
+ if (!name[len])
goto last_component;
+ name += len;
err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
if (err < 0)
@@ -1773,24 +1923,21 @@ static struct dentry *lookup_hash(struct nameidata *nd)
struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
struct qstr this;
- unsigned long hash;
unsigned int c;
WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
this.name = name;
this.len = len;
+ this.hash = full_name_hash(name, len);
if (!len)
return ERR_PTR(-EACCES);
- hash = init_name_hash();
while (len--) {
c = *(const unsigned char *)name++;
if (c == '/' || c == '\0')
return ERR_PTR(-EACCES);
- hash = partial_name_hash(c, hash);
}
- this.hash = end_name_hash(hash);
/*
* See if the low-level filesystem might want
* to use its own hash..
@@ -1825,7 +1972,7 @@ int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
int user_path_at(int dfd, const char __user *name, unsigned flags,
struct path *path)
{
- return user_path_at_empty(dfd, name, flags, path, 0);
+ return user_path_at_empty(dfd, name, flags, path, NULL);
}
static int user_path_parent(int dfd, const char __user *path,
@@ -2138,7 +2285,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
/* sayonara */
error = complete_walk(nd);
if (error)
- return ERR_PTR(-ECHILD);
+ return ERR_PTR(error);
error = -ENOTDIR;
if (nd->flags & LOOKUP_DIRECTORY) {
@@ -2237,7 +2384,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
error = complete_walk(nd);
if (error)
- goto exit;
+ return ERR_PTR(error);
error = -EISDIR;
if (S_ISDIR(nd->inode->i_mode))
goto exit;
@@ -2545,6 +2692,7 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, d
int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
int error = may_create(dir, dentry);
+ unsigned max_links = dir->i_sb->s_max_links;
if (error)
return error;
@@ -2557,6 +2705,9 @@ int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
if (error)
return error;
+ if (max_links && dir->i_nlink >= max_links)
+ return -EMLINK;
+
error = dir->i_op->mkdir(dir, dentry, mode);
if (!error)
fsnotify_mkdir(dir, dentry);
@@ -2887,6 +3038,7 @@ SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newn
int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
{
struct inode *inode = old_dentry->d_inode;
+ unsigned max_links = dir->i_sb->s_max_links;
int error;
if (!inode)
@@ -2917,6 +3069,8 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
/* Make sure we don't allow creating hardlink to an unlinked file */
if (inode->i_nlink == 0)
error = -ENOENT;
+ else if (max_links && inode->i_nlink >= max_links)
+ error = -EMLINK;
else
error = dir->i_op->link(old_dentry, dir, new_dentry);
mutex_unlock(&inode->i_mutex);
@@ -3026,6 +3180,7 @@ static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
{
int error = 0;
struct inode *target = new_dentry->d_inode;
+ unsigned max_links = new_dir->i_sb->s_max_links;
/*
* If we are going to change the parent - check write permissions,
@@ -3049,6 +3204,11 @@ static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
goto out;
+ error = -EMLINK;
+ if (max_links && !target && new_dir != old_dir &&
+ new_dir->i_nlink >= max_links)
+ goto out;
+
if (target)
shrink_dcache_parent(new_dentry);
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
@@ -3347,9 +3507,9 @@ retry:
if (err)
goto fail;
- kaddr = kmap_atomic(page, KM_USER0);
+ kaddr = kmap_atomic(page);
memcpy(kaddr, symname, len-1);
- kunmap_atomic(kaddr, KM_USER0);
+ kunmap_atomic(kaddr);
err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
page, fsdata);
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.