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apparmor: Move path lookup to using preallocated buffers

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Dynamically allocating buffers is problematic and is an extra layer
that is a potntial point of failure and can slow down mediation.
Change path lookup to use the preallocated per cpu buffers.

Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
John Johansen
2017-05-23 03:25:14 -07:00
parent 72c8a76864
commit 4227c333f6
4 changed files with 53 additions and 86 deletions
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114
security/apparmor/path.c
View File

@@ -79,7 +79,6 @@ static int disconnect(const struct path *path, char *buf, char **name,
* d_namespace_path - lookup a name associated with a given path
* @path: path to lookup (NOT NULL)
* @buf: buffer to store path to (NOT NULL)
* @buflen: length of @buf
* @name: Returns - pointer for start of path name with in @buf (NOT NULL)
* @flags: flags controlling path lookup
* @disconnected: string to prefix to disconnected paths
@@ -90,12 +89,14 @@ static int disconnect(const struct path *path, char *buf, char **name,
* When no error the path name is returned in @name which points to
* to a position in @buf
*/
static int d_namespace_path(const struct path *path, char *buf, int buflen,
char **name, int flags, const char *disconnected)
static int d_namespace_path(const struct path *path, char *buf, char **name,
int flags, const char *disconnected)
{
char *res;
int error = 0;
int connected = 1;
int isdir = (flags & PATH_IS_DIR) ? 1 : 0;
int buflen = aa_g_path_max - isdir;
if (path->mnt->mnt_flags & MNT_INTERNAL) {
/* it's not mounted anywhere */
@@ -110,10 +111,12 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen,
/* TODO: convert over to using a per namespace
* control instead of hard coded /proc
*/
return prepend(name, *name - buf, "/proc", 5);
error = prepend(name, *name - buf, "/proc", 5);
goto out;
} else
return disconnect(path, buf, name, flags,
disconnected);
error = disconnect(path, buf, name, flags,
disconnected);
goto out;
}
/* resolve paths relative to chroot?*/
@@ -132,8 +135,11 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen,
* be returned.
*/
if (!res || IS_ERR(res)) {
if (PTR_ERR(res) == -ENAMETOOLONG)
return -ENAMETOOLONG;
if (PTR_ERR(res) == -ENAMETOOLONG) {
error = -ENAMETOOLONG;
*name = buf;
goto out;
}
connected = 0;
res = dentry_path_raw(path->dentry, buf, buflen);
if (IS_ERR(res)) {
@@ -146,6 +152,9 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen,
*name = res;
if (!connected)
error = disconnect(path, buf, name, flags, disconnected);
/* Handle two cases:
* 1. A deleted dentry && profile is not allowing mediation of deleted
* 2. On some filesystems, newly allocated dentries appear to the
@@ -153,62 +162,27 @@ static int d_namespace_path(const struct path *path, char *buf, int buflen,
* allocated.
*/
if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
!(flags & PATH_MEDIATE_DELETED)) {
!(flags & (PATH_MEDIATE_DELETED | PATH_DELEGATE_DELETED))) {
error = -ENOENT;
goto out;
}
if (!connected)
error = disconnect(path, buf, name, flags, disconnected);
out:
return error;
}
/**
* get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
* @path: path to get name for (NOT NULL)
* @flags: flags controlling path lookup
* @buffer: buffer to put name in (NOT NULL)
* @size: size of buffer
* @name: Returns - contains position of path name in @buffer (NOT NULL)
*
* Returns: %0 else error on failure
*/
static int get_name_to_buffer(const struct path *path, int flags, char *buffer,
int size, char **name, const char **info,
const char *disconnected)
{
int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
int error = d_namespace_path(path, buffer, size - adjust, name, flags,
disconnected);
if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
/*
* Append "/" to the pathname. The root directory is a special
* case; it already ends in slash.
*/
strcpy(&buffer[size - 2], "/");
if (info && error) {
if (error == -ENOENT)
*info = "Failed name lookup - deleted entry";
else if (error == -EACCES)
*info = "Failed name lookup - disconnected path";
else if (error == -ENAMETOOLONG)
*info = "Failed name lookup - name too long";
else
*info = "Failed name lookup";
}
/*
* Append "/" to the pathname. The root directory is a special
* case; it already ends in slash.
*/
if (!error && isdir && ((*name)[1] != '\0' || (*name)[0] != '/'))
strcpy(&buf[aa_g_path_max - 2], "/");
return error;
}
/**
* aa_path_name - compute the pathname of a file
* aa_path_name - get the pathname to a buffer ensure dir / is appended
* @path: path the file (NOT NULL)
* @flags: flags controlling path name generation
* @buffer: buffer that aa_get_name() allocated (NOT NULL)
* @buffer: buffer to put name in (NOT NULL)
* @name: Returns - the generated path name if !error (NOT NULL)
* @info: Returns - information on why the path lookup failed (MAYBE NULL)
* @disconnected: string to prepend to disconnected paths
@@ -224,33 +198,23 @@ static int get_name_to_buffer(const struct path *path, int flags, char *buffer,
*
* Returns: %0 else error code if could retrieve name
*/
int aa_path_name(const struct path *path, int flags, char **buffer,
int aa_path_name(const struct path *path, int flags, char *buffer,
const char **name, const char **info, const char *disconnected)
{
char *buf, *str = NULL;
int size = 256;
int error;
char *str = NULL;
int error = d_namespace_path(path, buffer, &str, flags, disconnected);
*name = NULL;
*buffer = NULL;
for (;;) {
/* freed by caller */
buf = kmalloc(size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
error = get_name_to_buffer(path, flags, buf, size, &str, info,
disconnected);
if (error != -ENAMETOOLONG)
break;
kfree(buf);
size <<= 1;
if (size > aa_g_path_max)
return -ENAMETOOLONG;
*info = NULL;
if (info && error) {
if (error == -ENOENT)
*info = "Failed name lookup - deleted entry";
else if (error == -EACCES)
*info = "Failed name lookup - disconnected path";
else if (error == -ENAMETOOLONG)
*info = "Failed name lookup - name too long";
else
*info = "Failed name lookup";
}
*buffer = buf;
*name = str;
return error;