wireguard-linux/fs/tracefs, branch update-toolchain

tracefs: Use generic inode RCU for synchronizing freeing

2024-08-08T00:27:49Z

With structure layout randomization enabled for 'struct inode' we need to avoid overlapping any of the RCU-used / initialized-only-once members, e.g. i_lru or i_sb_list to not corrupt related list traversals when making use of the rcu_head. For an unlucky structure layout of 'struct inode' we may end up with the following splat when running the ftrace selftests: [<...>] list_del corruption, ffff888103ee2cb0->next (tracefs_inode_cache+0x0/0x4e0 [slab object]) is NULL (prev is tracefs_inode_cache+0x78/0x4e0 [slab object]) [<...>] ------------[ cut here ]------------ [<...>] kernel BUG at lib/list_debug.c:54! [<...>] invalid opcode: 0000 [#1] PREEMPT SMP KASAN [<...>] CPU: 3 PID: 2550 Comm: mount Tainted: G N 6.8.12-grsec+ #122 ed2f536ca62f28b087b90e3cc906a8d25b3ddc65 [<...>] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [<...>] RIP: 0010:[] __list_del_entry_valid_or_report+0x138/0x3e0 [<...>] Code: 48 b8 99 fb 65 f2 ff ff ff ff e9 03 5c d9 fc cc 48 b8 99 fb 65 f2 ff ff ff ff e9 33 5a d9 fc cc 48 b8 99 fb 65 f2 ff ff ff ff <0f> 0b 4c 89 e9 48 89 ea 48 89 ee 48 c7 c7 60 8f dd 89 31 c0 e8 2f [<...>] RSP: 0018:fffffe80416afaf0 EFLAGS: 00010283 [<...>] RAX: 0000000000000098 RBX: ffff888103ee2cb0 RCX: 0000000000000000 [<...>] RDX: ffffffff84655fe8 RSI: ffffffff89dd8b60 RDI: 0000000000000001 [<...>] RBP: ffff888103ee2cb0 R08: 0000000000000001 R09: fffffbd0082d5f25 [<...>] R10: fffffe80416af92f R11: 0000000000000001 R12: fdf99c16731d9b6d [<...>] R13: 0000000000000000 R14: ffff88819ad4b8b8 R15: 0000000000000000 [<...>] RBX: tracefs_inode_cache+0x0/0x4e0 [slab object] [<...>] RDX: __list_del_entry_valid_or_report+0x108/0x3e0 [<...>] RSI: __func__.47+0x4340/0x4400 [<...>] RBP: tracefs_inode_cache+0x0/0x4e0 [slab object] [<...>] RSP: process kstack fffffe80416afaf0+0x7af0/0x8000 [mount 2550 2550] [<...>] R09: kasan shadow of process kstack fffffe80416af928+0x7928/0x8000 [mount 2550 2550] [<...>] R10: process kstack fffffe80416af92f+0x792f/0x8000 [mount 2550 2550] [<...>] R14: tracefs_inode_cache+0x78/0x4e0 [slab object] [<...>] FS: 00006dcb380c1840(0000) GS:ffff8881e0600000(0000) knlGS:0000000000000000 [<...>] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [<...>] CR2: 000076ab72b30e84 CR3: 000000000b088004 CR4: 0000000000360ef0 shadow CR4: 0000000000360ef0 [<...>] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [<...>] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [<...>] ASID: 0003 [<...>] Stack: [<...>] ffffffff818a2315 00000000f5c856ee ffffffff896f1840 ffff888103ee2cb0 [<...>] ffff88812b6b9750 0000000079d714b6 fffffbfff1e9280b ffffffff8f49405f [<...>] 0000000000000001 0000000000000000 ffff888104457280 ffffffff8248b392 [<...>] Call Trace: [<...>] [<...>] [] ? lock_release+0x175/0x380 fffffe80416afaf0 [<...>] [] list_lru_del+0x152/0x740 fffffe80416afb48 [<...>] [] list_lru_del_obj+0x113/0x280 fffffe80416afb88 [<...>] [] ? _atomic_dec_and_lock+0x119/0x200 fffffe80416afb90 [<...>] [] iput_final+0x1c4/0x9a0 fffffe80416afbb8 [<...>] [] dentry_unlink_inode+0x44b/0xaa0 fffffe80416afbf8 [<...>] [] __dentry_kill+0x23c/0xf00 fffffe80416afc40 [<...>] [] ? __this_cpu_preempt_check+0x1f/0xa0 fffffe80416afc48 [<...>] [] ? shrink_dentry_list+0x1c5/0x760 fffffe80416afc70 [<...>] [] ? shrink_dentry_list+0x51/0x760 fffffe80416afc78 [<...>] [] shrink_dentry_list+0x288/0x760 fffffe80416afc80 [<...>] [] shrink_dcache_sb+0x155/0x420 fffffe80416afcc8 [<...>] [] ? debug_smp_processor_id+0x23/0xa0 fffffe80416afce0 [<...>] [] ? do_one_tree+0x140/0x140 fffffe80416afcf8 [<...>] [] ? do_remount+0x329/0xa00 fffffe80416afd18 [<...>] [] ? security_sb_remount+0x81/0x1c0 fffffe80416afd38 [<...>] [] reconfigure_super+0x856/0x14e0 fffffe80416afd70 [<...>] [] ? ns_capable_common+0xe7/0x2a0 fffffe80416afd90 [<...>] [] do_remount+0x416/0xa00 fffffe80416afdd0 [<...>] [] path_mount+0x5c4/0x900 fffffe80416afe28 [<...>] [] ? finish_automount+0x13a0/0x13a0 fffffe80416afe60 [<...>] [] ? user_path_at_empty+0xb2/0x140 fffffe80416afe88 [<...>] [] do_mount+0x115/0x1c0 fffffe80416afeb8 [<...>] [] ? path_mount+0x900/0x900 fffffe80416afed8 [<...>] [] ? __kasan_check_write+0x1c/0xa0 fffffe80416afee0 [<...>] [] __do_sys_mount+0x12f/0x280 fffffe80416aff30 [<...>] [] __x64_sys_mount+0xcd/0x2e0 fffffe80416aff70 [<...>] [] ? syscall_trace_enter+0x218/0x380 fffffe80416aff88 [<...>] [] x64_sys_call+0x5d5e/0x6720 fffffe80416affa8 [<...>] [] do_syscall_64+0xcd/0x3c0 fffffe80416affb8 [<...>] [] entry_SYSCALL_64_safe_stack+0x4c/0x87 fffffe80416affe8 [<...>] [<...>] [<...>] RIP: 0033:[<00006dcb382ff66a>] vm_area_struct[mount 2550 2550 file 6dcb38225000-6dcb3837e000 22 55(read|exec|mayread|mayexec)]+0x0/0xb8 [userland map] [<...>] Code: 48 8b 0d 29 18 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f6 17 0d 00 f7 d8 64 89 01 48 [<...>] RSP: 002b:0000763d68192558 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 [<...>] RAX: ffffffffffffffda RBX: 00006dcb38433264 RCX: 00006dcb382ff66a [<...>] RDX: 000017c3e0d11210 RSI: 000017c3e0d1a5a0 RDI: 000017c3e0d1ae70 [<...>] RBP: 000017c3e0d10fb0 R08: 000017c3e0d11260 R09: 00006dcb383d1be0 [<...>] R10: 000000000020002e R11: 0000000000000246 R12: 0000000000000000 [<...>] R13: 000017c3e0d1ae70 R14: 000017c3e0d11210 R15: 000017c3e0d10fb0 [<...>] RBX: vm_area_struct[mount 2550 2550 file 6dcb38433000-6dcb38434000 5b 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] RCX: vm_area_struct[mount 2550 2550 file 6dcb38225000-6dcb3837e000 22 55(read|exec|mayread|mayexec)]+0x0/0xb8 [userland map] [<...>] RDX: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] RSI: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] RDI: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] RBP: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] RSP: vm_area_struct[mount 2550 2550 anon 763d68173000-763d68195000 7ffffffdd 100133(read|write|mayread|maywrite|growsdown|account)]+0x0/0xb8 [userland map] [<...>] R08: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] R09: vm_area_struct[mount 2550 2550 file 6dcb383d1000-6dcb383d3000 1cd 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] R13: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] R14: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] R15: vm_area_struct[mount 2550 2550 anon 17c3e0d0f000-17c3e0d31000 17c3e0d0f 100033(read|write|mayread|maywrite|account)]+0x0/0xb8 [userland map] [<...>] [<...>] Modules linked in: [<...>] ---[ end trace 0000000000000000 ]--- The list debug message as well as RBX's symbolic value point out that the object in question was allocated from 'tracefs_inode_cache' and that the list's '->next' member is at offset 0. Dumping the layout of the relevant parts of 'struct tracefs_inode' gives the following: struct tracefs_inode { union { struct inode { struct list_head { struct list_head * next; /* 0 8 */ struct list_head * prev; /* 8 8 */ } i_lru; [...] } vfs_inode; struct callback_head { void (*func)(struct callback_head *); /* 0 8 */ struct callback_head * next; /* 8 8 */ } rcu; }; [...] }; Above shows that 'vfs_inode.i_lru' overlaps with 'rcu' which will destroy the 'i_lru' list as soon as the 'rcu' member gets used, e.g. in call_rcu() or later when calling the RCU callback. This will disturb concurrent list traversals as well as object reuse which assumes these list heads will keep their integrity. For reproduction, the following diff manually overlays 'i_lru' with 'rcu' as, otherwise, one would require some good portion of luck for gambling an unlucky RANDSTRUCT seed: --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -629,6 +629,7 @@ struct inode { umode_t i_mode; unsigned short i_opflags; kuid_t i_uid; + struct list_head i_lru; /* inode LRU list */ kgid_t i_gid; unsigned int i_flags; @@ -690,7 +691,6 @@ struct inode { u16 i_wb_frn_avg_time; u16 i_wb_frn_history; #endif - struct list_head i_lru; /* inode LRU list */ struct list_head i_sb_list; struct list_head i_wb_list; /* backing dev writeback list */ union { The tracefs inode does not need to supply its own RCU delayed destruction of its inode. The inode code itself offers both a "destroy_inode()" callback that gets called when the last reference of the inode is released, and the "free_inode()" which is called after a RCU synchronization period from the "destroy_inode()". The tracefs code can unlink the inode from its list in the destroy_inode() callback, and the simply free it from the free_inode() callback. This should provide the same protection. Link: https://lore.kernel.org/all/20240807115143.45927-3-minipli@grsecurity.net/ Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Ajay Kaher Cc: Ilkka =?utf-8?b?TmF1bGFww6TDpA==?= Link: https://lore.kernel.org/20240807185402.61410544@gandalf.local.home Fixes: baa23a8d4360 ("tracefs: Reset permissions on remount if permissions are options") Reported-by: Mathias Krause Reported-by: Brad Spengler Suggested-by: Al Viro Signed-off-by: Steven Rostedt (Google)

eventfs: Use SRCU for freeing eventfs_inodes

2024-08-07T23:28:48Z

To mirror the SRCU lock held in eventfs_iterate() when iterating over eventfs inodes, use call_srcu() to free them too. This was accidentally(?) degraded to RCU in commit 43aa6f97c2d0 ("eventfs: Get rid of dentry pointers without refcounts"). Cc: Ajay Kaher Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Linus Torvalds Cc: stable@vger.kernel.org Link: https://lore.kernel.org/20240723210755.8970-1-minipli@grsecurity.net Fixes: 43aa6f97c2d0 ("eventfs: Get rid of dentry pointers without refcounts") Signed-off-by: Mathias Krause Signed-off-by: Steven Rostedt (Google)

eventfs: Don't return NULL in eventfs_create_dir()

2024-08-07T23:28:31Z

Commit 77a06c33a22d ("eventfs: Test for ei->is_freed when accessing ei->dentry") added another check, testing if the parent was freed after we released the mutex. If so, the function returns NULL. However, all callers expect it to either return a valid pointer or an error pointer, at least since commit 5264a2f4bb3b ("tracing: Fix a NULL vs IS_ERR() bug in event_subsystem_dir()"). Returning NULL will therefore fail the error condition check in the caller. Fix this by substituting the NULL return value with a fitting error pointer. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: stable@vger.kernel.org Fixes: 77a06c33a22d ("eventfs: Test for ei->is_freed when accessing ei->dentry") Link: https://lore.kernel.org/20240723122522.2724-1-minipli@grsecurity.net Reviewed-by: Dan Carpenter Reviewed-by: Ajay Kaher Signed-off-by: Mathias Krause Signed-off-by: Steven Rostedt (Google)

tracefs: Fix inode allocation

2024-08-07T22:49:06Z

The leading comment above alloc_inode_sb() is pretty explicit about it: /* * This must be used for allocating filesystems specific inodes to set * up the inode reclaim context correctly. */ Switch tracefs over to alloc_inode_sb() to make sure inodes are properly linked. Cc: Ajay Kaher Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Al Viro Cc: stable@vger.kernel.org Link: https://lore.kernel.org/20240807115143.45927-2-minipli@grsecurity.net Fixes: ba37ff75e04b ("eventfs: Implement tracefs_inode_cache") Signed-off-by: Mathias Krause Signed-off-by: Steven Rostedt (Google)

tracefs: Convert to new uid/gid option parsing helpers

2024-07-02T04:21:20Z

Convert to new uid/gid option parsing helpers Signed-off-by: Eric Sandeen Link: https://lore.kernel.org/r/6c9b0b16-e61b-4dfc-852d-e2eb5bb11b82@redhat.com Acked-by: Steven Rostedt (Google) Signed-off-by: Christian Brauner

eventfs: Do not use attributes for events directory

2024-05-23T13:31:50Z

The top "events" directory has a static inode (it's created when it is and removed when the directory is removed). There's no need to use the events ei->attr to determine its permissions. But it is used for saving the permissions of the "events" directory for when it is created, as that is needed for the default permissions for the files and directories underneath it. For example: # cd /sys/kernel/tracing # mkdir instances/foo # chown 1001 instances/foo/events The files under instances/foo/events should still have the same owner as instances/foo (which the instances/foo/events ei->attr will hold), but the events directory now has owner 1001. Link: https://lore.kernel.org/lkml/20240522165032.104981011@goodmis.org Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Signed-off-by: Steven Rostedt (Google)

eventfs: Cleanup permissions in creation of inodes

2024-05-23T13:31:50Z

The permissions being set during the creation of the inodes was updating eventfs_inode attributes as well. Those attributes should only be touched by the setattr or remount operations, not during the creation of inodes. The eventfs_inode attributes should only be used to set the inodes and should not be modified during the inode creation. Simplify the code and fix the situation by: 1) Removing the eventfs_find_events() and doing a simple lookup for the events descriptor in eventfs_get_inode() 2) Remove update_events_attr() as the attributes should only be used to update the inode and should not be modified here. 3) Add update_inode_attr() that uses the attributes to determine what the inode permissions should be. 4) As the parent_inode of the eventfs_root_inode structure is no longer needed, remove it. Now on creation, the inode gets the proper permissions without causing side effects to the ei->attr field. Link: https://lore.kernel.org/lkml/20240522165031.944088388@goodmis.org Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Signed-off-by: Steven Rostedt (Google)

eventfs: Remove getattr and permission callbacks

2024-05-23T13:27:25Z

Now that inodes have their permissions updated on remount, the only other places to update the inode permissions are when they are created and in the setattr callback. The getattr and permission callbacks are not needed as the inodes should already be set at their proper settings. Remove the callbacks, as it not only simplifies the code, but also allows more flexibility to fix the inconsistencies with various corner cases (like changing the permission of an instance directory). Link: https://lore.kernel.org/lkml/20240522165031.782066021@goodmis.org Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Signed-off-by: Steven Rostedt (Google)

eventfs: Consolidate the eventfs_inode update in eventfs_get_inode()

2024-05-23T13:27:25Z

To simplify the code, create a eventfs_get_inode() that is used when an eventfs file or directory is created. Have the internal tracefs_inode updated the appropriate flags in this function and update the inode's mode as well. Link: https://lore.kernel.org/lkml/20240522165031.624864160@goodmis.org Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Signed-off-by: Steven Rostedt (Google)

tracefs: Clear EVENT_INODE flag in tracefs_drop_inode()

2024-05-23T13:26:24Z

When the inode is being dropped from the dentry, the TRACEFS_EVENT_INODE flag needs to be cleared to prevent a remount from calling eventfs_remount() on the tracefs_inode private data. There's a race between the inode is dropped (and the dentry freed) to where the inode is actually freed. If a remount happens between the two, the eventfs_inode could be accessed after it is freed (only the dentry keeps a ref count on it). Currently the TRACEFS_EVENT_INODE flag is cleared from the dentry iput() function. But this is incorrect, as it is possible that the inode has another reference to it. The flag should only be cleared when the inode is really being dropped and has no more references. That happens in the drop_inode callback of the inode, as that gets called when the last reference of the inode is released. Remove the tracefs_d_iput() function and move its logic to the more appropriate tracefs_drop_inode() callback function. Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.908205106@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Masahiro Yamada Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options") Signed-off-by: Steven Rostedt (Google)