CVE-2023-52900 Information

Description

In the Linux kernel the following vulnerability has been resolved:

nilfs2: fix general protection fault in nilfs_btree_insert()

If nilfs2 reads a corrupted disk image and tries to reads a b-tree node block by calling __nilfs_btree_get_block() against an invalid virtual block address it returns -ENOENT because conversion of the virtual block address to a disk block address fails. However this return value is the same as the internal code that b-tree lookup routines return to indicate that the block being searched does not exist so functions that operate on that b-tree may misbehave.

When nilfs_btree_insert() receives this spurious ’not found’ code from nilfs_btree_do_lookup() it misunderstands that the ’not found’ check was successful and continues the insert operation using incomplete lookup path data causing the following crash:

general protection fault probably for non-canonical address 0xdffffc0000000005: 0000 [1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] … RIP: 0010:nilfs_btree_get_nonroot_node fs/nilfs2/btree.c:418 [inline] RIP: 0010:nilfs_btree_prepare_insert fs/nilfs2/btree.c:1077 [inline] RIP: 0010:nilfs_btree_insert+0x6d3/0x1c10 fs/nilfs2/btree.c:1238 Code: bc 24 80 00 00 00 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 ff e8 4b 02 92 fe 4d 8b 3f 49 83 c7 28 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 ff e8 2e 02 92 fe 4d 8b 3f 49 83 c7 02 … Call Trace: nilfs_bmap_do_insert fs/nilfs2/bmap.c:121 [inline] nilfs_bmap_insert+0x20d/0x360 fs/nilfs2/bmap.c:147 nilfs_get_block+0x414/0x8d0 fs/nilfs2/inode.c:101 __block_write_begin_int+0x54c/0x1a80 fs/buffer.c:1991 __block_write_begin fs/buffer.c:2041 [inline] block_write_begin+0x93/0x1e0 fs/buffer.c:2102 nilfs_write_begin+0x9c/0x110 fs/nilfs2/inode.c:261 generic_perform_write+0x2e4/0x5e0 mm/filemap.c:3772 __generic_file_write_iter+0x176/0x400 mm/filemap.c:3900 generic_file_write_iter+0xab/0x310 mm/filemap.c:3932 call_write_iter include/linux/fs.h:2186 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x7dc/0xc50 fs/read_write.c:584 ksys_write+0x177/0x2a0 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd …

This patch fixes the root cause of this problem by replacing the error code that __nilfs_btree_get_block() returns on block address conversion failure from -ENOENT to another internal code -EINVAL which means that the b-tree metadata is corrupted.

By returning -EINVAL it propagates without glitches and for all relevant b-tree operations functions in the upper bmap layer output an error message indicating corrupted b-tree metadata via nilfs_bmap_convert_error() and code -EIO will be eventually returned as it should be.

Reference

https://git.kernel.org/stable/c/3c2a2ff67d46106715c2132021b98bd057c27545 https://git.kernel.org/stable/c/d9fde9eab1766170ff2ade67d09178d2cfd78749 https://git.kernel.org/stable/c/b0ba060d3287108eba17603bee3810e4cf2c272d https://git.kernel.org/stable/c/712bd74eccb9d3626a0a236641962eca8e11a243 https://git.kernel.org/stable/c/45627a1a6450662e1e0f8174ef07b05710a20062 https://git.kernel.org/stable/c/0bf463939c09e5b2c35c71ed74a5fd60a74d6a04 https://git.kernel.org/stable/c/7633355e5c7f29c049a9048e461427d1d8ed3051