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Currently when rmdir on an instance is done, eventfs_remove_events_dir()
is called and it does a dput on the dentry and then frees the
eventfs_inode that represents the events directory.
But there's no protection against a reader reading the top level events
directory at the same time and we can get a use after free error. Instead,
use the dput() associated to the dentry to also free the eventfs_inode
associated to the events directory, as that will get called when the last
reference to the directory is released.
This issue triggered the following KASAN report:
==================================================================
BUG: KASAN: slab-use-after-free in eventfs_root_lookup+0x88/0x1b0
Read of size 8 at addr ffff888120130ca0 by task ftracetest/1201
CPU: 4 PID: 1201 Comm: ftracetest Not tainted 6.5.0-test-10737-g469e0a8194e7 #13
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x57/0x90
print_report+0xcf/0x670
? __pfx_ring_buffer_record_off+0x10/0x10
? _raw_spin_lock_irqsave+0x2b/0x70
? __virt_addr_valid+0xd9/0x160
kasan_report+0xd4/0x110
? eventfs_root_lookup+0x88/0x1b0
? eventfs_root_lookup+0x88/0x1b0
eventfs_root_lookup+0x88/0x1b0
? eventfs_root_lookup+0x33/0x1b0
__lookup_slow+0x194/0x2a0
? __pfx___lookup_slow+0x10/0x10
? down_read+0x11c/0x330
walk_component+0x166/0x220
link_path_walk.part.0.constprop.0+0x3a3/0x5a0
? seqcount_lockdep_reader_access+0x82/0x90
? __pfx_link_path_walk.part.0.constprop.0+0x10/0x10
path_openat+0x143/0x11f0
? __lock_acquire+0xa1a/0x3220
? __pfx_path_openat+0x10/0x10
? __pfx___lock_acquire+0x10/0x10
do_filp_open+0x166/0x290
? __pfx_do_filp_open+0x10/0x10
? lock_is_held_type+0xce/0x120
? preempt_count_sub+0xb7/0x100
? _raw_spin_unlock+0x29/0x50
? alloc_fd+0x1a0/0x320
do_sys_openat2+0x126/0x160
? rcu_is_watching+0x34/0x60
? __pfx_do_sys_openat2+0x10/0x10
? __might_resched+0x2cf/0x3b0
? __fget_light+0xdf/0x100
__x64_sys_openat+0xcd/0x140
? __pfx___x64_sys_openat+0x10/0x10
? syscall_enter_from_user_mode+0x22/0x90
? lockdep_hardirqs_on+0x7d/0x100
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
RIP: 0033:0x7f1dceef5e51
Code: 75 57 89 f0 25 00 00 41 00 3d 00 00 41 00 74 49 80 3d 9a 27 0e 00 00 74 6d 89 da 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 93 00 00 00 48 8b 54 24 28 64 48 2b 14 25
RSP: 002b:00007fff2cddf380 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000241 RCX: 00007f1dceef5e51
RDX: 0000000000000241 RSI: 000055d7520677d0 RDI: 00000000ffffff9c
RBP: 000055d7520677d0 R08: 000000000000001e R09: 0000000000000001
R10: 00000000000001b6 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000003 R14: 000055d752035678 R15: 000055d752067788
</TASK>
Allocated by task 1200:
kasan_save_stack+0x2f/0x50
kasan_set_track+0x21/0x30
__kasan_kmalloc+0x8b/0x90
eventfs_create_events_dir+0x54/0x220
create_event_toplevel_files+0x42/0x130
event_trace_add_tracer+0x33/0x180
trace_array_create_dir+0x52/0xf0
trace_array_create+0x361/0x410
instance_mkdir+0x6b/0xb0
tracefs_syscall_mkdir+0x57/0x80
vfs_mkdir+0x275/0x380
do_mkdirat+0x1da/0x210
__x64_sys_mkdir+0x74/0xa0
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
Freed by task 1251:
kasan_save_stack+0x2f/0x50
kasan_set_track+0x21/0x30
kasan_save_free_info+0x27/0x40
__kasan_slab_free+0x106/0x180
__kmem_cache_free+0x149/0x2e0
event_trace_del_tracer+0xcb/0x120
__remove_instance+0x16a/0x340
instance_rmdir+0x77/0xa0
tracefs_syscall_rmdir+0x77/0xc0
vfs_rmdir+0xed/0x2d0
do_rmdir+0x235/0x280
__x64_sys_rmdir+0x5f/0x90
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
The buggy address belongs to the object at ffff888120130ca0
which belongs to the cache kmalloc-16 of size 16
The buggy address is located 0 bytes inside of
freed 16-byte region [ffff888120130ca0, ffff888120130cb0)
The buggy address belongs to the physical page:
page:000000004dbddbb0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x120130
flags: 0x17ffffc0000800(slab|node=0|zone=2|lastcpupid=0x1fffff)
page_type: 0xffffffff()
raw: 0017ffffc0000800 ffff8881000423c0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000800080 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888120130b80: 00 00 fc fc 00 05 fc fc 00 00 fc fc 00 02 fc fc
ffff888120130c00: 00 07 fc fc 00 00 fc fc 00 00 fc fc fa fb fc fc
>ffff888120130c80: 00 00 fc fc fa fb fc fc 00 00 fc fc 00 00 fc fc
^
ffff888120130d00: 00 00 fc fc 00 00 fc fc 00 00 fc fc fa fb fc fc
ffff888120130d80: 00 00 fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
==================================================================
Link: https://lkml.kernel.org/r/20230907024803.250873643@goodmis.org
Link: https://lore.kernel.org/all/1cb3aee2-19af-c472-e265-05176fe9bd84@huawei.com/
Cc: Ajay Kaher <akaher@vmware.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 5bdcd5f533 eventfs: ("Implement removal of meta data from eventfs")
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
31 lines
1.0 KiB
C
31 lines
1.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _TRACEFS_INTERNAL_H
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#define _TRACEFS_INTERNAL_H
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enum {
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TRACEFS_EVENT_INODE = BIT(1),
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TRACEFS_EVENT_TOP_INODE = BIT(2),
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};
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struct tracefs_inode {
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unsigned long flags;
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void *private;
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struct inode vfs_inode;
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};
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static inline struct tracefs_inode *get_tracefs(const struct inode *inode)
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{
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return container_of(inode, struct tracefs_inode, vfs_inode);
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}
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struct dentry *tracefs_start_creating(const char *name, struct dentry *parent);
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struct dentry *tracefs_end_creating(struct dentry *dentry);
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struct dentry *tracefs_failed_creating(struct dentry *dentry);
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struct inode *tracefs_get_inode(struct super_block *sb);
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struct dentry *eventfs_start_creating(const char *name, struct dentry *parent);
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struct dentry *eventfs_failed_creating(struct dentry *dentry);
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struct dentry *eventfs_end_creating(struct dentry *dentry);
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void eventfs_set_ef_status_free(struct tracefs_inode *ti, struct dentry *dentry);
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#endif /* _TRACEFS_INTERNAL_H */
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