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At btrfs_orphan_cleanup(), if we can't find an inode (btrfs_iget() returns
an -ENOENT error pointer), we proceed with 'ret' set to -ENOENT and the
inode pointer set to ERR_PTR(-ENOENT). Later when we proceed to the body
of the following if statement:
if (ret == -ENOENT || inode->i_nlink) {
(...)
trans = btrfs_start_transaction(root, 1);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
iput(inode);
goto out;
}
(...)
ret = btrfs_del_orphan_item(trans, root,
found_key.objectid);
btrfs_end_transaction(trans);
if (ret) {
iput(inode);
goto out;
}
continue;
}
If we get an error from btrfs_start_transaction() or from the call to
btrfs_del_orphan_item() we end calling iput() against an inode pointer
that has a value of ERR_PTR(-ENOENT), resulting in a crash with the
following trace:
[876.667] BUG: kernel NULL pointer dereference, address: 0000000000000096
[876.667] #PF: supervisor read access in kernel mode
[876.667] #PF: error_code(0x0000) - not-present page
[876.667] PGD 0 P4D 0
[876.668] Oops: 0000 [#1] PREEMPT SMP PTI
[876.668] CPU: 0 PID: 2356187 Comm: mount Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1
[876.668] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
[876.668] RIP: 0010:iput+0xa/0x20
[876.668] Code: ff ff ff 66 (...)
[876.669] RSP: 0018:ffffafa9c0c9f9d0 EFLAGS: 00010282
[876.669] RAX: ffffffffffffffe4 RBX: 000000000009453b RCX: 0000000000000000
[876.669] RDX: 0000000000000001 RSI: ffffafa9c0c9f930 RDI: fffffffffffffffe
[876.669] RBP: ffff95c612f3b800 R08: 0000000000000001 R09: ffffffffffffffe4
[876.670] R10: 00018f2a71010000 R11: 000000000ead96e3 R12: ffff95cb7d6909a0
[876.670] R13: fffffffffffffffe R14: ffff95c60f477000 R15: 00000000ffffffe4
[876.670] FS: 00007f5fbe30a840(0000) GS:ffff95ccdfa00000(0000) knlGS:0000000000000000
[876.670] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[876.671] CR2: 0000000000000096 CR3: 000000055e9f6004 CR4: 0000000000370ef0
[876.671] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[876.671] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[876.672] Call Trace:
[876.744] <TASK>
[876.744] ? __die_body+0x1b/0x60
[876.744] ? page_fault_oops+0x15d/0x450
[876.745] ? __kmem_cache_alloc_node+0x47/0x410
[876.745] ? do_user_addr_fault+0x65/0x8a0
[876.745] ? exc_page_fault+0x74/0x170
[876.746] ? asm_exc_page_fault+0x22/0x30
[876.746] ? iput+0xa/0x20
[876.746] btrfs_orphan_cleanup+0x221/0x330 [btrfs]
[876.746] btrfs_lookup_dentry+0x58f/0x5f0 [btrfs]
[876.747] btrfs_lookup+0xe/0x30 [btrfs]
[876.747] __lookup_slow+0x82/0x130
[876.785] walk_component+0xe5/0x160
[876.786] path_lookupat.isra.0+0x6e/0x150
[876.786] filename_lookup+0xcf/0x1a0
[876.786] ? mod_objcg_state+0xd2/0x360
[876.786] ? obj_cgroup_charge+0xf5/0x110
[876.787] ? should_failslab+0xa/0x20
[876.787] ? kmem_cache_alloc+0x47/0x450
[876.787] vfs_path_lookup+0x51/0x90
[876.788] mount_subtree+0x8d/0x130
[876.788] btrfs_mount+0x149/0x410 [btrfs]
[876.788] ? __kmem_cache_alloc_node+0x47/0x410
[876.788] ? vfs_parse_fs_param+0xc0/0x110
[876.789] legacy_get_tree+0x24/0x50
[876.834] vfs_get_tree+0x22/0xd0
[876.852] path_mount+0x2d8/0x9c0
[876.852] do_mount+0x79/0x90
[876.852] __x64_sys_mount+0x8e/0xd0
[876.853] do_syscall_64+0x38/0x90
[876.899] entry_SYSCALL_64_after_hwframe+0x72/0xdc
[876.958] RIP: 0033:0x7f5fbe50b76a
[876.959] Code: 48 8b 0d a9 (...)
[876.959] RSP: 002b:00007fff01925798 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
[876.959] RAX: ffffffffffffffda RBX: 00007f5fbe694264 RCX: 00007f5fbe50b76a
[876.960] RDX: 0000561bde6c8720 RSI: 0000561bde6bdec0 RDI: 0000561bde6c31a0
[876.960] RBP: 0000561bde6bdc70 R08: 0000000000000000 R09: 0000000000000001
[876.960] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[876.960] R13: 0000561bde6c31a0 R14: 0000561bde6c8720 R15: 0000561bde6bdc70
[876.960] </TASK>
So fix this by setting 'inode' to NULL whenever we get an error from
btrfs_iget(), and to make the code simpler, stop testing for 'ret' being
-ENOENT to check if we have an inode - instead test for 'inode' being NULL
or not. Having a NULL 'inode' prevents any iput() call from crashing, as
iput() ignores NULL inode pointers. Also, stop testing for a NULL return
value from btrfs_iget() with PTR_ERR_OR_ZERO(), because btrfs_iget() never
returns NULL - in case an inode is not found, it returns ERR_PTR(-ENOENT),
and in case of memory allocation failure, it returns ERR_PTR(-ENOMEM).
We also don't need the extra iput() calls on the error branches for the
btrfs_start_transaction() and btrfs_del_orphan_item() calls, as we have
already called iput() before, so remove them.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.