[yocto] [meta-selinux][PATCHv2 6/8] e2fsprogs: Copy xattr block from source file.

Philip Tricca flihp at twobit.us
Sat Sep 5 10:59:22 PDT 2015


Hey Joe,

Any thoughts on this? It looks like since my patch set went into master
the meta-selinux build is broken for a number of build hosts (anything
w/o linux-libc-headers). I think Jackie and I have worked out a solution
but it's waiting for a maintainer to merge (or reject).

I hate to think I'm breaking builds for some folks but we've made as
much progress as we can w/o a maintainer getting involved. Any help you
can provide would be appreciated.

Thanks,
Philip

On 08/23/2015 10:27 PM, Huang, Jie (Jackie) wrote:
> 
> 
>> -----Original Message-----
>> From: Philip Tricca [mailto:flihp at twobit.us]
>> Sent: Monday, August 24, 2015 6:25 AM
>> To: Huang, Jie (Jackie)
>> Cc: yocto at yoctoproject.org
>> Subject: Re: [yocto] [meta-selinux][PATCHv2 6/8] e2fsprogs: Copy xattr block from source file.
>>
>> Hello Jackie,
>>
>> On 08/20/2015 11:25 PM, Huang, Jie (Jackie) wrote:
>>>> -----Original Message-----
>>>> From: yocto-bounces at yoctoproject.org
>>>> [mailto:yocto-bounces at yoctoproject.org] On Behalf Of Philip Tricca
>>>> Sent: Thursday, June 18, 2015 6:31 AM
>>>> To: yocto at yoctoproject.org
>>>> Subject: [yocto] [meta-selinux][PATCHv2 6/8] e2fsprogs: Copy xattr block from source file.
>>>>
>>>> Signed-off-by: Philip Tricca <flihp at twobit.us>
>>>> ---
>>>>  .../e2fsprogs/misc-xattr-create-xattr-block.patch  | 341 +++++++++++++++++++++
>>>>  .../e2fsprogs/e2fsprogs_1.42.9.bbappend            |   1 +
>>>>  2 files changed, 342 insertions(+)
>>>>  create mode 100644
>>>> recipes-devtools/e2fsprogs/e2fsprogs/misc-xattr-create-xattr-block.pa
>>>> tch
>>>>
>>>> diff --git
>>>> a/recipes-devtools/e2fsprogs/e2fsprogs/misc-xattr-create-xattr-block.
>>>> patch b/recipes-
>>>> devtools/e2fsprogs/e2fsprogs/misc-xattr-create-xattr-block.patch
>>>> new file mode 100644
>>>> index 0000000..5955b44
>>>> --- /dev/null
>>>> +++ b/recipes-devtools/e2fsprogs/e2fsprogs/misc-xattr-create-xattr-bl
>>>> +++ ock
>>>> +++ .patch
>>>> @@ -0,0 +1,341 @@
>>>> +To build the xattr disk block we process the output from listxattr
>>>> +and lgetxattr from the source file system object. This data is
>>>> +formated in a disk block according to the format specified in the kernel ext2 file system driver.
>>>> +See the comment block at the beginning of fs/ext2/xattr.c for details.
>>>> +
>>>> +Currently we only process attributes with the 'security.' prefix as
>>>> +our use case is SELinux labels and IMA. Additional prefixes can
>>>> +likely be supported with minimal effort but none have been tested.
>>>> +
>>>> +Once the xattr block has been created it is written to disk. The
>>>> +xattr block is associated with the appropriate file system object
>>>> +through the i_file_acl inode member and the inode is updated on disk.
>>>> +
>>>> +Signed-off-by: Philip Tricca <flihp at twobit.us>
>>>> +
>>>> +Index: e2fsprogs-1.42.9/misc/xattr.c
>>>> +===================================================================
>>>> +--- e2fsprogs-1.42.9.orig/misc/xattr.c
>>>> ++++ e2fsprogs-1.42.9/misc/xattr.c
>>>> +@@ -1,6 +1,23 @@
>>>> + #include "xattr.h"
>>>> +
>>>> ++#include <attr/xattr.h>
>>>> ++#include <ctype.h>
>>>> ++#include <errno.h>
>>>> ++#include <ext2fs/ext2_ext_attr.h>
>>>> ++#include <linux/xattr.h>
>>>> ++#include <stdint.h>
>>>> + #include <stdio.h>
>>>> ++#include <stdlib.h>
>>>> ++#include <string.h>
>>>> ++#include <sys/stat.h>
>>>> ++#include <sys/types.h>
>>>> ++#include <unistd.h>
>>>> ++
>>>> ++#define MIN(X, Y) (((X) < (Y)) ? (X) : (Y)) #define HEADER(ptr)
>>>> ++((struct ext2_ext_attr_header *)(ptr)) #define ENTRY(ptr)  ((struct
>>>> ++ext2_ext_attr_entry *)(ptr)) #define FIRST_ENTRY(ptr)
>>>> ++ENTRY(HEADER(ptr) + 1) #define VALUE(hdr, ent) (((char*)hdr) +
>>>> ++(ent->e_value_offs))
>>>> +
>>>> + #ifdef XATTR_DEBUG
>>>> + #define XATTR_STDERR(fmt, args...) fprintf (stderr, fmt, ##args) @@
>>>> +-8,6 +25,28 @@  #define XATTR_STDERR(fmt, args...) do {} while (0)
>>>> +#endif
>>>> +
>>>> ++/* structure for mapping xattr name prefix data */ typedef struct
>>>> ++xattr_prefix {
>>>> ++	int index;
>>>> ++	char *name;
>>>> ++	size_t length;
>>>> ++} xattr_prefix_t;
>>>> ++
>>>> ++xattr_prefix_t xattr_prefixes [] = {
>>>> ++/* Only interested in security prefix. Can support others though.
>>>> ++	{
>>>> ++		.index = EXT2_XATTR_INDEX_USER,
>>>> ++		.name = XATTR_USER_PREFIX,
>>>> ++		.length = XATTR_USER_PREFIX_LEN,
>>>> ++	},
>>>> ++*/
>>>> ++	{
>>>> ++		.index = EXT2_XATTR_INDEX_SECURITY,
>>>> ++		.name = XATTR_SECURITY_PREFIX,
>>>> ++		.length = XATTR_SECURITY_PREFIX_LEN,
>>>
>>> Hi Philip,
>>>
>>> This cause build errors on some host OS when building e2fsprogs-native:
>>>
>>> | /build/yp/y_x64_150821/tmp/work/x86_64-linux/e2fsprogs-native/1.42.9-r0/e2fsprogs-
>> 1.42.9/debugfs/../misc/xattr.c:62:11: error: 'XATTR_SECURITY_PREFIX' undeclared here (not in a
>> function)
>>> |    .name = XATTR_SECURITY_PREFIX,
>>> |            ^
>>> | /build/yp/y_x64_150821/tmp/work/x86_64-linux/e2fsprogs-native/1.42.9-r0/e2fsprogs-
>> 1.42.9/debugfs/../misc/xattr.c:63:13: error: 'XATTR_SECURITY_PREFIX_LEN' undeclared here (not in a
>> function)
>>> |    .length = XATTR_SECURITY_PREFIX_LEN,
>>> |              ^
>>>
>>> I did some investigate and found that your patch needs the header
>>> linux/xattr.h, which is provided by linux-libc-headers, but for
>>> -native package, there is no linux-libc-headers-native, so it search
>>> the one from host OS, but the problem is, there is no XATTR_SECURITY_PREFIX definition in the
>> linux/xattr.h on some host OS like: SUSE 11.x, centos 6, etc.
>>>
>>> I'm not sure if your patch is really needed by the e2fsprogs-native,
>>> if not, I think we can make this patch only apply for target package.
>>> If yes, you may need to make it avoid the dependency on host's header or you may have a better
>> idea about this.
>>
>> I took a look at this yesterday. Creating a bbappend for linux-libc-headers and adding 'native' to
>> BBCLASSEXTEND seems like the most direct fix. Add a new dependency to the e2fsprogs package and I
>> think the issue is resolved. I'll send patches to the list and if you're willing to test them I'd appreciate it.
> 
> I tested with your patch and it works fine, thanks!
> 
> Thanks,
> Jackie
> 
>>
>> Thanks,
>> Philip
>>
>>>> ++	},
>>>> ++	{ 0 },
>>>> ++};
>>>> +
>>>> + /* Free remaining resources after all files have been processed. */
>>>> +void @@ -16,6 +55,211 @@ xattr_cleanup ()
>>>> + 	XATTR_STDERR ("Cleaning up resources from xattrs.\n");  }
>>>> +
>>>> ++/* Get value for named xattr from file at path.
>>>> ++ * Returns pointer to allocated block for value and length in length param.
>>>> ++ * If no value, return NULL pointer and length of 0.
>>>> ++ * On error return NULL pointer and length set to -1.
>>>> ++ */
>>>> ++static char*
>>>> ++xattr_get_value (const char *path, const char *name, ssize_t
>>>> ++*length) {
>>>> ++	char *value = NULL;
>>>> ++
>>>> ++	*length = lgetxattr (path, name, NULL, 0);
>>>> ++	if (*length == -1) {
>>>> ++		com_err (__func__, errno, "lgetattr");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	if (*length == 0) {
>>>> ++		fprintf (stderr, "xattr %s has value length 0\n", name);
>>>> ++		goto out;
>>>> ++	}
>>>> ++	value = calloc (1, *length);
>>>> ++	if (value == NULL) {
>>>> ++		com_err (__func__, errno, "calloc");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	*length = lgetxattr (path, name, value, *length);
>>>> ++	if (*length == -1) {
>>>> ++		com_err (__func__, errno, "lgetattr");
>>>> ++		goto value_err;
>>>> ++	}
>>>> ++out:
>>>> ++	return value;
>>>> ++
>>>> ++value_err:
>>>> ++	if (value)
>>>> ++		free (value);
>>>> ++	return NULL;
>>>> ++}
>>>> ++
>>>> ++/* Get all attribute names for file at path. Return pointer to
>>>> ++allocated memory
>>>> ++ * block holding all names and the length through parameter size.
>>>> ++ * If no xattrs: return NULL and set size to 0
>>>> ++ * If error: return NULL and set size to -1  */ static char*
>>>> ++xattr_get_names (const char *path, ssize_t *size) {
>>>> ++	char *names = NULL;
>>>> ++
>>>> ++	*size = llistxattr (path, NULL, 0);
>>>> ++	if (*size == -1) {
>>>> ++		com_err (__func__, errno, "llistxattr");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	if (*size == 0) {
>>>> ++		/* no xattrs */
>>>> ++		goto out;
>>>> ++	}
>>>> ++	names = calloc (1, *size);
>>>> ++	if (names == NULL) {
>>>> ++		com_err (__func__, errno, "calloc");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	*size = llistxattr (path, names, *size);
>>>> ++	if (*size == -1) {
>>>> ++		com_err (__func__, errno, "llistxattr");
>>>> ++		goto cleanup;
>>>> ++	}
>>>> ++	if (*size == 0) {
>>>> ++		fprintf (stdout, "Conflicting data, no xattrs for file: %s\n", path);
>>>> ++		goto cleanup;
>>>> ++	}
>>>> ++out:
>>>> ++	return names;
>>>> ++
>>>> ++cleanup:
>>>> ++	if (names)
>>>> ++		free (names);
>>>> ++	return NULL;
>>>> ++}
>>>> ++
>>>> ++/* return pointer to next string in xattr name block, don't go
>>>> ++beyond length  */ static inline char* next_name (char *name, size_t length) {
>>>> ++	int i = 0;
>>>> ++
>>>> ++	for (i = 0; i < length; ++i)
>>>> ++		if (name [i] == '\0') {
>>>> ++			++i;
>>>> ++			break;
>>>> ++		}
>>>> ++
>>>> ++	return name + i;
>>>> ++}
>>>> ++
>>>> ++/* Find entry in xattr_table with matching prefix. */ static const
>>>> ++xattr_prefix_t* xattr_find_prefix (char *name, size_t length) {
>>>> ++	int i = 0;
>>>> ++
>>>> ++	XATTR_STDERR ("find_attr_data: searching for prefix from xattr name: %s\n", name);
>>>> ++	for (i = 0; xattr_prefixes[i].index != 0; ++i) {
>>>> ++		if (!strncmp (name, xattr_prefixes[i].name, MIN (length, xattr_prefixes[i].length))) {
>>>> ++			XATTR_STDERR ("found match in table with index: %d\n",
>>>> xattr_prefixes[i].index);
>>>> ++			return &xattr_prefixes[i];
>>>> ++		}
>>>> ++	}
>>>> ++	return NULL;
>>>> ++}
>>>> ++
>>>> ++/* Query file at path for attributes. build up structure the file
>>>> ++system
>>>> ++ * expects of an extended attribute disk block (header parameter).
>>>> ++ *
>>>> ++ * The main loop walks through the xattr names one at a time. It
>>>> ++gets the value
>>>> ++ * for each named xattr and copies the data into the xattr block
>>>> ++pointed to by
>>>> ++ * the header parameter. To do this the loop also tracks the
>>>> ++location of the
>>>> ++ * associated entry and value. Values start at the end of the
>>>> ++buffer and grow
>>>> ++ * back towards the header while the entries start immediately
>>>> ++after the header
>>>> ++ * and grow towards the end of the block.
>>>> ++ *
>>>> ++ * See the comment block at the beginning of the xattr.c file in
>>>> ++the
>>>> ++ext2 file
>>>> ++ * system code in the kernel: fs/ext2/xattr.c
>>>> ++ * Assume the xattr block pointed to by header parameter is initialized to 0s.
>>>> ++ */
>>>> ++static int
>>>> ++xattr_build_block (const char *path,
>>>> ++		struct ext2_ext_attr_header **header,
>>>> ++		size_t header_length)
>>>> ++{
>>>> ++	struct ext2_ext_attr_entry *entry = NULL;
>>>> ++	char *names = NULL, *value = NULL, *name_curr = NULL;
>>>> ++	ssize_t names_length = 0, value_length = 0;
>>>> ++	size_t name_length = 0, value_index = 0, len_rem = 0;
>>>> ++	const xattr_prefix_t *prefix = NULL;
>>>> ++	int ret = 0;
>>>> ++
>>>> ++	XATTR_STDERR ("xattr_build_block for file: %s\n", path);
>>>> ++	*header = NULL;
>>>> ++	names = xattr_get_names (path, &names_length);
>>>> ++	if (names == NULL) {
>>>> ++		// no xattrs for file @ path or error
>>>> ++		ret = names_length;
>>>> ++		goto out;
>>>> ++	}
>>>> ++	*header = calloc (1, header_length);
>>>> ++	if (*header == NULL) {
>>>> ++		com_err (__func__, errno, "calloc");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	(*header)->h_magic = EXT2_EXT_ATTR_MAGIC;
>>>> ++	(*header)->h_blocks = 1;
>>>> ++	/* Values start at end of buffer. NOTE: It must be moved before a value can
>>>> ++	 * be stored.
>>>> ++	 */
>>>> ++	value_index = header_length;
>>>> ++	for (name_curr = names, entry = FIRST_ENTRY(*header), len_rem = names_length;
>>>> ++		name_curr < names + names_length;
>>>> ++		len_rem = names_length - (name_curr - names),
>>>> ++			name_curr = next_name (name_curr, len_rem),
>>>> ++			entry = EXT2_EXT_ATTR_NEXT(entry))
>>>> ++	{
>>>> ++		XATTR_STDERR ("xattr_build_block: processing xattr with name %s\n", name_curr);
>>>> ++		name_length = strnlen (name_curr, len_rem);
>>>> ++		prefix = xattr_find_prefix (name_curr, name_length);
>>>> ++		if (!prefix) {
>>>> ++			fprintf (stderr, "Don't currently handle xattr: %s\n", name_curr);
>>>> ++			continue;
>>>> ++		}
>>>> ++		value = xattr_get_value (path, name_curr, &value_length);
>>>> ++		if (value == NULL) {
>>>> ++			// no xattr value or error
>>>> ++			fprintf (stderr, "failed to get value, skipping\n");
>>>> ++			goto next;
>>>> ++		}
>>>> ++		/* setup offsets and lengths for name and value */
>>>> ++		entry->e_name_len = name_length - prefix->length;
>>>> ++		entry->e_name_index = prefix->index;
>>>> ++		/* Can't know these till we know the length of the value. */
>>>> ++		entry->e_value_offs = value_index -= EXT2_EXT_ATTR_SIZE(value_length);
>>>> ++		entry->e_value_size = value_length;
>>>> ++		/* Check to be sure entry name and value don't overlap before copy. */
>>>> ++		if (EXT2_EXT_ATTR_NAME(entry) + entry->e_name_len > VALUE(*header, entry)) {
>>>> ++			fprintf (stderr, "xattr entry name and value overlap! Too much xattr data.");
>>>> ++			ret = -1;
>>>> ++			goto out;
>>>> ++		}
>>>> ++		/* copy name and value data then calculate the hash */
>>>> ++		memcpy (EXT2_EXT_ATTR_NAME(entry),
>>>> ++			name_curr + prefix->length,
>>>> ++			entry->e_name_len);
>>>> ++		memcpy (VALUE(*header, entry), value, entry->e_value_size);
>>>> ++		entry->e_hash = ext2fs_ext_attr_hash_entry (entry, VALUE(*header,
>>>> ++entry));
>>>> ++next:
>>>> ++		if (value)
>>>> ++			free (value);
>>>> ++	}
>>>> ++	XATTR_STDERR ("xattr_build_block: done building xattr buffer\n");
>>>> ++out:
>>>> ++	if (names)
>>>> ++		free (names);
>>>> ++	return ret;
>>>> ++}
>>>> ++
>>>> + /* This is the entry point to the xattr module. This function
>>>> +copies the xattrs
>>>> +  * from the file at 'path' to the file system object at 'ino'.
>>>> +  *
>>>> +@@ -28,7 +272,56 @@ errcode_t
>>>> + set_inode_xattr (ext2_filsys fs, ext2_ino_t ino, const char *path)  {
>>>> + 	errcode_t ret = 0;
>>>> ++	char *buf = NULL;
>>>> ++	struct ext2_inode inode = { 0 };
>>>> ++	blk_t block = 0;
>>>> ++	struct ext2_ext_attr_header *header = NULL;
>>>> ++	uint32_t newcount = 0;
>>>> +
>>>> + 	XATTR_STDERR ("Copying xattrs from %s to inode 0x%x.\n", path,
>>>> + ino);
>>>> ++	/* Populate the xattr block for the file at path */
>>>> ++	if (ret = xattr_build_block (path, &header, fs->blocksize)) {
>>>> ++		goto out;
>>>> ++	}
>>>> ++	if (header == NULL) {
>>>> ++		XATTR_STDERR ("set_inode_xattrs: no xattrs for %s\n", path);
>>>> ++		goto out;
>>>> ++	}
>>>> ++	if (ret = ext2fs_read_inode (fs, ino, &inode)) {
>>>> ++		com_err(__func__, ret, "ext2fs_read_inode");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	if (ret = ext2fs_alloc_block (fs, 0, NULL, &block)) {
>>>> ++		com_err(__func__, ret, "ext2fs_alloc_block: returned %d", ret);
>>>> ++		goto out;
>>>> ++	}
>>>> ++	ext2fs_mark_block_bitmap2 (fs->block_map, block);
>>>> ++	XATTR_STDERR ("writing xattr block 0x%x to disk:\n", block);
>>>> ++	if (ret = ext2fs_write_ext_attr (fs, block, header)) {
>>>> ++		com_err(__func__, ret, "ext2fs_write_ext_attr: returned %d", ret);
>>>> ++		goto out;
>>>> ++	}
>>>> ++	/* point inode for current file to xattr block, update block count and
>>>> ++	 * write inode to disk
>>>> ++	 */
>>>> ++	inode.i_file_acl = block;
>>>> ++	if (ret = ext2fs_adjust_ea_refcount2(fs,
>>>> ++					block,
>>>> ++					(char*)header,
>>>> ++					1,
>>>> ++					&newcount))
>>>> ++	{
>>>> ++		com_err(__func__, ret, "ext2fs_adjust_ea_refcount");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	if (ret = ext2fs_iblk_add_blocks (fs, &inode, 1)) {
>>>> ++		com_err(__func__, ret, "ext2fs_iblk_add_blocks failed");
>>>> ++		goto out;
>>>> ++	}
>>>> ++	if (ret = ext2fs_write_inode (fs, ino, &inode))
>>>> ++		com_err(__func__, ret, "ext2fs_write_inode: returned %d", ret);
>>>> ++out:
>>>> ++	if (header)
>>>> ++		free (header);
>>>> + 	return ret;
>>>> + }
>>>> diff --git a/recipes-devtools/e2fsprogs/e2fsprogs_1.42.9.bbappend
>>>> b/recipes- devtools/e2fsprogs/e2fsprogs_1.42.9.bbappend
>>>> index a4576b1..edc94d8 100644
>>>> --- a/recipes-devtools/e2fsprogs/e2fsprogs_1.42.9.bbappend
>>>> +++ b/recipes-devtools/e2fsprogs/e2fsprogs_1.42.9.bbappend
>>>> @@ -4,4 +4,5 @@ SRC_URI += " \
>>>>      file://misc-xattr-add-xattr-module-stub.patch \
>>>>      file://mke2fs.c-create_inode.c-copy-xattrs.patch \
>>>>      file://lib-ext2fs-ext2_ext_attr.h-add-xattr-index.patch \
>>>> +    file://misc-xattr-create-xattr-block.patch \
>>>>  "
>>>> --
>>>> 2.1.4
>>>>
>>>> --
>>>> _______________________________________________
>>>> yocto mailing list
>>>> yocto at yoctoproject.org
>>>> https://lists.yoctoproject.org/listinfo/yocto
> 




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