1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
2 From: Erwan Velu <erwanaliasr1@gmail.com>
3 Date: Wed, 25 Aug 2021 15:31:52 +0200
4 Subject: [PATCH] fs/xfs: Fix unreadable filesystem with v4 superblock
6 The commit 8b1e5d193 (fs/xfs: Add bigtime incompat feature support)
7 introduced the bigtime support by adding some features in v3 inodes.
8 This change extended grub_xfs_inode struct by 76 bytes but also changed
9 the computation of XFS_V2_INODE_SIZE and XFS_V3_INODE_SIZE. Prior this
10 commit, XFS_V2_INODE_SIZE was 100 bytes. After the commit it's 84 bytes
11 XFS_V2_INODE_SIZE becomes 16 bytes too small.
13 As a result, the data structures aren't properly aligned and the GRUB
14 generates "attempt to read or write outside of partition" errors when
15 trying to read the XFS filesystem:
19 grub> set debug=efi,gpt,xfs
22 partmap/gpt.c:93: Read a valid GPT header
23 partmap/gpt.c:115: GPT entry 0: start=4096, length=1953125
24 fs/xfs.c:931: Reading sb
25 fs/xfs.c:270: Validating superblock
26 fs/xfs.c:295: XFS v4 superblock detected
27 fs/xfs.c:962: Reading root ino 128
28 fs/xfs.c:515: Reading inode (128) - 64, 0
29 fs/xfs.c:515: Reading inode (739521961424144223) - 344365866970255880, 3840
30 error: attempt to read or write outside of partition.
32 This commit change the XFS_V2_INODE_SIZE computation by subtracting 76
33 bytes instead of 92 bytes from the actual size of grub_xfs_inode struct.
34 This 76 bytes value comes from added members:
35 20 grub_uint8_t unused5
36 1 grub_uint64_t flags2
37 48 grub_uint8_t unused6
39 This patch explicitly splits the v2 and v3 parts of the structure.
40 The unused4 is still ending of the v2 structures and the v3 starts
41 at unused5. Thanks to this we will avoid future corruptions of v2
44 The XFS_V2_INODE_SIZE is returning to its expected size and the
45 filesystem is back to a readable state:
49 grub> set debug=efi,gpt,xfs
52 partmap/gpt.c:93: Read a valid GPT header
53 partmap/gpt.c:115: GPT entry 0: start=4096, length=1953125
54 fs/xfs.c:931: Reading sb
55 fs/xfs.c:270: Validating superblock
56 fs/xfs.c:295: XFS v4 superblock detected
57 fs/xfs.c:962: Reading root ino 128
58 fs/xfs.c:515: Reading inode (128) - 64, 0
59 fs/xfs.c:515: Reading inode (128) - 64, 0
60 fs/xfs.c:931: Reading sb
61 fs/xfs.c:270: Validating superblock
62 fs/xfs.c:295: XFS v4 superblock detected
63 fs/xfs.c:962: Reading root ino 128
64 fs/xfs.c:515: Reading inode (128) - 64, 0
65 fs/xfs.c:515: Reading inode (128) - 64, 0
66 fs/xfs.c:515: Reading inode (128) - 64, 0
67 fs/xfs.c:515: Reading inode (131) - 64, 768
68 efi/ fs/xfs.c:515: Reading inode (3145856) - 1464904, 0
69 grub2/ fs/xfs.c:515: Reading inode (132) - 64, 1024
70 grub/ fs/xfs.c:515: Reading inode (139) - 64, 2816
73 Fixes: 8b1e5d193 (fs/xfs: Add bigtime incompat feature support)
75 Signed-off-by: Erwan Velu <e.velu@criteo.com>
76 Tested-by: Carlos Maiolino <cmaiolino@redhat.com>
77 Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
78 (cherry picked from commit a4b495520e4dc41a896a8b916a64eda9970c50ea)
80 grub-core/fs/xfs.c | 14 ++++++++++----
81 1 file changed, 10 insertions(+), 4 deletions(-)
83 diff --git a/grub-core/fs/xfs.c b/grub-core/fs/xfs.c
84 index 0f524c3a8a..e3816d1ec4 100644
85 --- a/grub-core/fs/xfs.c
86 +++ b/grub-core/fs/xfs.c
87 @@ -192,6 +192,11 @@ struct grub_xfs_time_legacy
88 grub_uint32_t nanosec;
92 + * The struct grub_xfs_inode layout was taken from the
93 + * struct xfs_dinode_core which is described here:
94 + * https://mirrors.edge.kernel.org/pub/linux/utils/fs/xfs/docs/xfs_filesystem_structure.pdf
98 grub_uint8_t magic[2];
99 @@ -208,14 +213,15 @@ struct grub_xfs_inode
100 grub_uint32_t nextents;
101 grub_uint16_t unused3;
102 grub_uint8_t fork_offset;
103 - grub_uint8_t unused4[37];
104 + grub_uint8_t unused4[17]; /* Last member of inode v2. */
105 + grub_uint8_t unused5[20]; /* First member of inode v3. */
106 grub_uint64_t flags2;
107 - grub_uint8_t unused5[48];
108 + grub_uint8_t unused6[48]; /* Last member of inode v3. */
111 #define XFS_V3_INODE_SIZE sizeof(struct grub_xfs_inode)
112 -/* Size of struct grub_xfs_inode until fork_offset (included). */
113 -#define XFS_V2_INODE_SIZE (XFS_V3_INODE_SIZE - 92)
114 +/* Size of struct grub_xfs_inode v2, up to unused4 member included. */
115 +#define XFS_V2_INODE_SIZE (XFS_V3_INODE_SIZE - 76)
117 struct grub_xfs_dirblock_tail