[PATCH v6 2/2] erofs-utils: fsck: introduce exporting xattrs

[Hongzhen Luo]

The current `fsck --extract` does not support exporting the extended
attributes of files. This patch adds `--xattrs` option to dump the
extended attributes, as well as the `--no-xattrs` option to not dump
the extended attributes.

Signed-off-by: Hongzhen Luo <hongzhen at linux.alibaba.com>
---
v6:
  - update man/fsck.erofs.1;
  - do not export non-`user.` namespace xattrs when operating
    as a non-privileged user;
  - use lsetxattr() to set xattrs instead of setxattr().

v5: https://lore.kernel.org/all/20240906022206.2725584-1-hongzhen@linux.alibaba.com/
v4: https://lore.kernel.org/all/20240905113723.1937634-1-hongzhen@linux.alibaba.com/
v3: https://lore.kernel.org/all/20240903113729.3539578-1-hongzhen@linux.alibaba.com/
v2: https://lore.kernel.org/all/20240903085643.3393012-1-hongzhen@linux.alibaba.com/
v1: https://lore.kernel.org/all/20240903073517.3311407-1-hongzhen@linux.alibaba.com/
---
 fsck/main.c      | 90 +++++++++++++++++++++++++++++++++++++++++++++---
 man/fsck.erofs.1 |  3 ++
 2 files changed, 89 insertions(+), 4 deletions(-)

diff --git a/fsck/main.c b/fsck/main.c
index 28f1e7e..e89c43d 100644
--- a/fsck/main.c
+++ b/fsck/main.c
@@ -9,10 +9,12 @@
 #include <utime.h>
 #include <unistd.h>
 #include <sys/stat.h>
+#include <sys/xattr.h>
 #include "erofs/print.h"
 #include "erofs/compress.h"
 #include "erofs/decompress.h"
 #include "erofs/dir.h"
+#include "erofs/xattr.h"
 #include "../lib/compressor.h"
 
 static int erofsfsck_check_inode(erofs_nid_t pnid, erofs_nid_t nid);
@@ -31,6 +33,7 @@ struct erofsfsck_cfg {
 	bool overwrite;
 	bool preserve_owner;
 	bool preserve_perms;
+	bool dump_xattrs;
 };
 static struct erofsfsck_cfg fsckcfg;
 
@@ -48,6 +51,8 @@ static struct option long_options[] = {
 	{"no-preserve-owner", no_argument, 0, 10},
 	{"no-preserve-perms", no_argument, 0, 11},
 	{"offset", required_argument, 0, 12},
+	{"xattrs", no_argument, 0, 13},
+	{"no-xattrs", no_argument, 0, 14},
 	{0, 0, 0, 0},
 };
 
@@ -98,6 +103,7 @@ static void usage(int argc, char **argv)
 		" --extract[=X]          check if all files are well encoded, optionally\n"
 		"                        extract to X\n"
 		" --offset=#             skip # bytes at the beginning of IMAGE\n"
+		" --[no-]xattrs          whether to dump extended attributes (default on)\n"
 		"\n"
 		" -a, -A, -y             no-op, for compatibility with fsck of other filesystems\n"
 		"\n"
@@ -225,6 +231,12 @@ static int erofsfsck_parse_options_cfg(int argc, char **argv)
 				return -EINVAL;
 			}
 			break;
+		case 13:
+			fsckcfg.dump_xattrs = true;
+			break;
+		case 14:
+			fsckcfg.dump_xattrs = false;
+			break;
 		default:
 			return -EINVAL;
 		}
@@ -411,6 +423,67 @@ out:
 	return ret;
 }
 
+static int erofsfsck_dump_xattrs(struct erofs_inode *inode)
+{
+	char *keylst, *key;
+	ssize_t kllen;
+	int ret;
+
+	kllen = erofs_listxattr(inode, NULL, 0);
+	if (kllen <= 0)
+		return kllen;
+	keylst = malloc(kllen);
+	if (!keylst)
+		return -ENOMEM;
+	ret = erofs_listxattr(inode, keylst, kllen);
+	if (ret != kllen) {
+		ret = -EINVAL;
+		goto out;
+	}
+	ret = 0;
+	for (key = keylst; key < keylst + kllen; key += strlen(key) + 1) {
+		void *value = NULL;
+		size_t size = 0;
+
+		if (!fsckcfg.superuser && erofs_xattr_prefix_index(key)
+		    != EROFS_XATTR_INDEX_USER)
+			continue;
+
+		ret = erofs_getxattr(inode, key, NULL, 0);
+		if (ret < 0)
+			break;
+		if (ret) {
+			size = ret;
+			value = malloc(size);
+			if (!value) {
+				ret = -ENOMEM;
+				break;
+			}
+			ret = erofs_getxattr(inode, key, value, size);
+			if (ret < 0) {
+				erofs_err("fail to get xattr %s @ nid %llu",
+					  key, inode->nid | 0ULL);
+				free(value);
+				break;
+			}
+			if (fsckcfg.extract_path)
+				ret = lsetxattr(fsckcfg.extract_path, key, value,
+						size, 0);
+			else
+				ret = 0;
+			free(value);
+			if (ret) {
+				erofs_err("fail to set xattr %s @ nid %llu",
+					  key, inode->nid | 0ULL);
+				break;
+			}
+		}
+	}
+out:
+	free(keylst);
+	return ret;
+}
+
 static int erofs_verify_inode_data(struct erofs_inode *inode, int outfd)
 {
 	struct erofs_map_blocks map = {
@@ -900,15 +973,23 @@ static int erofsfsck_check_inode(erofs_nid_t pnid, erofs_nid_t nid)
 		goto out;
 	}
 
-	/* verify xattr field */
-	ret = erofs_verify_xattr(&inode);
-	if (ret)
-		goto out;
+	if (!fsckcfg.check_decomp) {
+		/* verify xattr field */
+		ret = erofs_verify_xattr(&inode);
+		if (ret)
+			goto out;
+	}
 
 	ret = erofsfsck_extract_inode(&inode);
 	if (ret && ret != -ECANCELED)
 		goto out;
 
+	if (fsckcfg.check_decomp && fsckcfg.dump_xattrs) {
+		ret = erofsfsck_dump_xattrs(&inode);
+		if (ret)
+			return ret;
+	}
+
 	/* XXXX: the dir depth should be restricted in order to avoid loops */
 	if (S_ISDIR(inode.i_mode)) {
 		struct erofs_dir_context ctx = {
@@ -955,6 +1036,7 @@ int main(int argc, char *argv[])
 	fsckcfg.overwrite = false;
 	fsckcfg.preserve_owner = fsckcfg.superuser;
 	fsckcfg.preserve_perms = fsckcfg.superuser;
+	fsckcfg.dump_xattrs = true;
 
 	err = erofsfsck_parse_options_cfg(argc, argv);
 	if (err) {
diff --git a/man/fsck.erofs.1 b/man/fsck.erofs.1
index 393ae9e..898f48e 100644
--- a/man/fsck.erofs.1
+++ b/man/fsck.erofs.1
@@ -27,6 +27,9 @@ You may give multiple
 .B --device
 options in the correct order.
 .TP
+.BI "--[no-]xattrs"
+Whether to dump extended attributes (default on).
+.TP
 .BI "\-\-extract" "[=directory]"
 Test to extract the whole file system. It scans all inode data, including
 compressed inode data, which leads to more I/O and CPU load, so it might
-- 
2.43.5