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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Erwan Velu <erwanaliasr1@gmail.com>
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Date: Wed, 25 Aug 2021 15:31:52 +0200
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Subject: [PATCH] fs/xfs: Fix unreadable filesystem with v4 superblock
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The commit 8b1e5d193 (fs/xfs: Add bigtime incompat feature support)
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introduced the bigtime support by adding some features in v3 inodes.
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This change extended grub_xfs_inode struct by 76 bytes but also changed
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the computation of XFS_V2_INODE_SIZE and XFS_V3_INODE_SIZE. Prior this
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commit, XFS_V2_INODE_SIZE was 100 bytes. After the commit it's 84 bytes
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XFS_V2_INODE_SIZE becomes 16 bytes too small.
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As a result, the data structures aren't properly aligned and the GRUB
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generates "attempt to read or write outside of partition" errors when
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trying to read the XFS filesystem:
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GNU GRUB version 2.11
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....
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grub> set debug=efi,gpt,xfs
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grub> insmod part_gpt
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grub> ls (hd0,gpt1)/
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partmap/gpt.c:93: Read a valid GPT header
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partmap/gpt.c:115: GPT entry 0: start=4096, length=1953125
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fs/xfs.c:931: Reading sb
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fs/xfs.c:270: Validating superblock
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fs/xfs.c:295: XFS v4 superblock detected
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fs/xfs.c:962: Reading root ino 128
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fs/xfs.c:515: Reading inode (128) - 64, 0
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fs/xfs.c:515: Reading inode (739521961424144223) - 344365866970255880, 3840
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error: attempt to read or write outside of partition.
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This commit change the XFS_V2_INODE_SIZE computation by subtracting 76
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bytes instead of 92 bytes from the actual size of grub_xfs_inode struct.
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This 76 bytes value comes from added members:
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20 grub_uint8_t unused5
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1 grub_uint64_t flags2
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48 grub_uint8_t unused6
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This patch explicitly splits the v2 and v3 parts of the structure.
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The unused4 is still ending of the v2 structures and the v3 starts
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at unused5. Thanks to this we will avoid future corruptions of v2
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or v3 inodes.
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The XFS_V2_INODE_SIZE is returning to its expected size and the
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filesystem is back to a readable state:
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GNU GRUB version 2.11
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....
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grub> set debug=efi,gpt,xfs
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grub> insmod part_gpt
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grub> ls (hd0,gpt1)/
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partmap/gpt.c:93: Read a valid GPT header
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partmap/gpt.c:115: GPT entry 0: start=4096, length=1953125
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fs/xfs.c:931: Reading sb
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fs/xfs.c:270: Validating superblock
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fs/xfs.c:295: XFS v4 superblock detected
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fs/xfs.c:962: Reading root ino 128
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fs/xfs.c:515: Reading inode (128) - 64, 0
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fs/xfs.c:515: Reading inode (128) - 64, 0
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fs/xfs.c:931: Reading sb
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fs/xfs.c:270: Validating superblock
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fs/xfs.c:295: XFS v4 superblock detected
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fs/xfs.c:962: Reading root ino 128
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fs/xfs.c:515: Reading inode (128) - 64, 0
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fs/xfs.c:515: Reading inode (128) - 64, 0
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fs/xfs.c:515: Reading inode (128) - 64, 0
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fs/xfs.c:515: Reading inode (131) - 64, 768
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efi/ fs/xfs.c:515: Reading inode (3145856) - 1464904, 0
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grub2/ fs/xfs.c:515: Reading inode (132) - 64, 1024
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grub/ fs/xfs.c:515: Reading inode (139) - 64, 2816
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grub>
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Fixes: 8b1e5d193 (fs/xfs: Add bigtime incompat feature support)
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Signed-off-by: Erwan Velu <e.velu@criteo.com>
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Tested-by: Carlos Maiolino <cmaiolino@redhat.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit a4b495520e4dc41a896a8b916a64eda9970c50ea)
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---
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grub-core/fs/xfs.c | 14 ++++++++++----
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1 file changed, 10 insertions(+), 4 deletions(-)
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diff --git a/grub-core/fs/xfs.c b/grub-core/fs/xfs.c
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index 0f524c3a8a..e3816d1ec4 100644
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--- a/grub-core/fs/xfs.c
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+++ b/grub-core/fs/xfs.c
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@@ -192,6 +192,11 @@ struct grub_xfs_time_legacy
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grub_uint32_t nanosec;
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} GRUB_PACKED;
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+/*
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+ * The struct grub_xfs_inode layout was taken from the
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+ * struct xfs_dinode_core which is described here:
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+ * https://mirrors.edge.kernel.org/pub/linux/utils/fs/xfs/docs/xfs_filesystem_structure.pdf
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+ */
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struct grub_xfs_inode
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{
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grub_uint8_t magic[2];
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@@ -208,14 +213,15 @@ struct grub_xfs_inode
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grub_uint32_t nextents;
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grub_uint16_t unused3;
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grub_uint8_t fork_offset;
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- grub_uint8_t unused4[37];
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+ grub_uint8_t unused4[17]; /* Last member of inode v2. */
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+ grub_uint8_t unused5[20]; /* First member of inode v3. */
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grub_uint64_t flags2;
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- grub_uint8_t unused5[48];
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+ grub_uint8_t unused6[48]; /* Last member of inode v3. */
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} GRUB_PACKED;
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#define XFS_V3_INODE_SIZE sizeof(struct grub_xfs_inode)
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-/* Size of struct grub_xfs_inode until fork_offset (included). */
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-#define XFS_V2_INODE_SIZE (XFS_V3_INODE_SIZE - 92)
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+/* Size of struct grub_xfs_inode v2, up to unused4 member included. */
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+#define XFS_V2_INODE_SIZE (XFS_V3_INODE_SIZE - 76)
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struct grub_xfs_dirblock_tail
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{
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