landlock: walk parent dir without getting/putting #6
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This commit replaces dget_parent with a direct read of d_parent. By holding rcu read lock we should be safe in terms of not reading freed memory, but this is still problematic due to move+unlink, as will be shown with the test in the next commit. Note that follow_up is still used when walking up a mountpoint. Signed-off-by: Tingmao Wang <m@maowtm.org>
By not taking references to parent directories when walking, the dentry
can become negative under us, if the target file is moved then the parent
quickly deleted. This is problematic because it means that we lose access
to any landlock rules attached to that parent, and thus we won't be able
to grant the correct access even when we're allowed to pretend the move
hasn't happened yet.
This commit tests a slightly more complicated scenario, where after moving
the file's parent directory away, the next two intermediate directories
are quickly removed. This demonstrates that in this situation the only
choice for Landlock is to restart the walk. Without doing that, even if
we were to re-check d_parent, if we were "cut off" when we've already
walked away from the original leaf, we would still not be able to recover.
As an illustration:
mkdir /d1 /d1/d2 /b
create landlock rule on /d1
create landlock rule on /b
touch /d1/d2/file
thread 1 thread 2
cd /d1/d2
cat file
landlock walks to /d1/d2 without ref,
checked rule on /d1/d2 (nothing),
about to walk up to /d1
mv /d1/d2/file /b
rmdir /d1/d2 /d1
(/d1/d2 and /d1 both becomes negative)
notices stuff changed
at this point, we're looking at /d1/d2
and trying to walk to its parent.
however, both /d1/d2 and /d1 are negative
now.
Our only choice is to restart the walk
altogether from the original file's dentry,
which will now have d_parent /b.
The test is probablistic as it tests for a race condition, but I found
that in my environment, with the previous patch, it pretty much always
reliably fails within 10 seconds. I've set the timeout to 30 seconds, and
the test will pass if no permission errors (or other errors) detected. In
those 30 seconds it will keep recreating the above directory structure
(except with a lot more sibling directories so it can run for some time
before it "exhausts" all the directories and has to recreate the whole
thing).
Signed-off-by: Tingmao Wang <m@maowtm.org>
This fixes the issue mentioned in the previous patch, by essentially having two "modes" for the pathwalk code - in the pathwalk_ref == false case we don't take references and just inspect `d_parent` (unless we have to `follow_up`). In the pathwalk_ref == true case, this is the same as before. When we detect any renames during a pathwalk_ref == false walk, we restart with pathwalk_ref == true, re-initializing the layer masks. I'm not sure if this is completely correct in regards to is_dom_check - but seems to work for now. I can revisit this later. Signed-off-by: Tingmao Wang <m@maowtm.org>
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These iterations require the read lock, otherwise RCU lockdep will splat: ============================= WARNING: suspicious RCU usage 6.17.0-rc3-00014-g31419c045d64 #6 Tainted: G O ----------------------------- drivers/base/power/main.c:1333 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 5 locks held by rtcwake/547: #0: 00000000643ab418 (sb_writers#6){.+.+}-{0:0}, at: file_start_write+0x2b/0x3a #1: 0000000067a0ca88 (&of->mutex#2){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x181/0x24b #2: 00000000631eac40 (kn->active#3){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x191/0x24b #3: 00000000609a1308 (system_transition_mutex){+.+.}-{4:4}, at: pm_suspend+0xaf/0x30b #4: 0000000060c0fdb0 (device_links_srcu){.+.+}-{0:0}, at: device_links_read_lock+0x75/0x98 stack backtrace: CPU: 0 UID: 0 PID: 547 Comm: rtcwake Tainted: G O 6.17.0-rc3-00014-g31419c045d64 #6 VOLUNTARY Tainted: [O]=OOT_MODULE Stack: 223721b3a80 6089eac6 00000001 00000001 ffffff00 6089eac6 00000535 6086e528 721b3ac0 6003c294 00000000 60031fc0 Call Trace: [<600407ed>] show_stack+0x10e/0x127 [<6003c294>] dump_stack_lvl+0x77/0xc6 [<6003c2fd>] dump_stack+0x1a/0x20 [<600bc2f8>] lockdep_rcu_suspicious+0x116/0x13e [<603d8ea1>] dpm_async_suspend_superior+0x117/0x17e [<603d980f>] device_suspend+0x528/0x541 [<603da24b>] dpm_suspend+0x1a2/0x267 [<603da837>] dpm_suspend_start+0x5d/0x72 [<600ca0c9>] suspend_devices_and_enter+0xab/0x736 [...] Add the fourth argument to the iteration to annotate this and avoid the splat. Fixes: 0679963 ("PM: sleep: Make async suspend handle suppliers like parents") Fixes: ed18738 ("PM: sleep: Make async resume handle consumers like children") Signed-off-by: Johannes Berg <johannes.berg@intel.com> Link: https://patch.msgid.link/20250826134348.aba79f6e6299.I9ecf55da46ccf33778f2c018a82e1819d815b348@changeid Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
micromaomao
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Sep 21, 2025
Commit 0e2f80a("fs/dax: ensure all pages are idle prior to filesystem unmount") introduced the WARN_ON_ONCE to capture whether the filesystem has removed all DAX entries or not and applied the fix to xfs and ext4. Apply the missed fix on erofs to fix the runtime warning: [ 5.266254] ------------[ cut here ]------------ [ 5.266274] WARNING: CPU: 6 PID: 3109 at mm/truncate.c:89 truncate_folio_batch_exceptionals+0xff/0x260 [ 5.266294] Modules linked in: [ 5.266999] CPU: 6 UID: 0 PID: 3109 Comm: umount Tainted: G S 6.16.0+ #6 PREEMPT(voluntary) [ 5.267012] Tainted: [S]=CPU_OUT_OF_SPEC [ 5.267017] Hardware name: Dell Inc. OptiPlex 5000/05WXFV, BIOS 1.5.1 08/24/2022 [ 5.267024] RIP: 0010:truncate_folio_batch_exceptionals+0xff/0x260 [ 5.267076] Code: 00 00 41 39 df 7f 11 eb 78 83 c3 01 49 83 c4 08 41 39 df 74 6c 48 63 f3 48 83 fe 1f 0f 83 3c 01 00 00 43 f6 44 26 08 01 74 df <0f> 0b 4a 8b 34 22 4c 89 ef 48 89 55 90 e8 ff 54 1f 00 48 8b 55 90 [ 5.267083] RSP: 0018:ffffc900013f36c8 EFLAGS: 00010202 [ 5.267095] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 5.267101] RDX: ffffc900013f3790 RSI: 0000000000000000 RDI: ffff8882a1407898 [ 5.267108] RBP: ffffc900013f3740 R08: 0000000000000000 R09: 0000000000000000 [ 5.267113] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 5.267119] R13: ffff8882a1407ab8 R14: ffffc900013f3888 R15: 0000000000000001 [ 5.267125] FS: 00007aaa8b437800(0000) GS:ffff88850025b000(0000) knlGS:0000000000000000 [ 5.267132] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 5.267138] CR2: 00007aaa8b3aac10 CR3: 000000024f764000 CR4: 0000000000f52ef0 [ 5.267144] PKRU: 55555554 [ 5.267150] Call Trace: [ 5.267154] <TASK> [ 5.267181] truncate_inode_pages_range+0x118/0x5e0 [ 5.267193] ? save_trace+0x54/0x390 [ 5.267296] truncate_inode_pages_final+0x43/0x60 [ 5.267309] evict+0x2a4/0x2c0 [ 5.267339] dispose_list+0x39/0x80 [ 5.267352] evict_inodes+0x150/0x1b0 [ 5.267376] generic_shutdown_super+0x41/0x180 [ 5.267390] kill_block_super+0x1b/0x50 [ 5.267402] erofs_kill_sb+0x81/0x90 [erofs] [ 5.267436] deactivate_locked_super+0x32/0xb0 [ 5.267450] deactivate_super+0x46/0x60 [ 5.267460] cleanup_mnt+0xc3/0x170 [ 5.267475] __cleanup_mnt+0x12/0x20 [ 5.267485] task_work_run+0x5d/0xb0 [ 5.267499] exit_to_user_mode_loop+0x144/0x170 [ 5.267512] do_syscall_64+0x2b9/0x7c0 [ 5.267523] ? __lock_acquire+0x665/0x2ce0 [ 5.267535] ? __lock_acquire+0x665/0x2ce0 [ 5.267560] ? lock_acquire+0xcd/0x300 [ 5.267573] ? find_held_lock+0x31/0x90 [ 5.267582] ? mntput_no_expire+0x97/0x4e0 [ 5.267606] ? mntput_no_expire+0xa1/0x4e0 [ 5.267625] ? mntput+0x24/0x50 [ 5.267634] ? path_put+0x1e/0x30 [ 5.267647] ? do_faccessat+0x120/0x2f0 [ 5.267677] ? do_syscall_64+0x1a2/0x7c0 [ 5.267686] ? from_kgid_munged+0x17/0x30 [ 5.267703] ? from_kuid_munged+0x13/0x30 [ 5.267711] ? __do_sys_getuid+0x3d/0x50 [ 5.267724] ? do_syscall_64+0x1a2/0x7c0 [ 5.267732] ? irqentry_exit+0x77/0xb0 [ 5.267743] ? clear_bhb_loop+0x30/0x80 [ 5.267752] ? clear_bhb_loop+0x30/0x80 [ 5.267765] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 5.267772] RIP: 0033:0x7aaa8b32a9fb [ 5.267781] Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 31 f6 e9 05 00 00 00 0f 1f 44 00 00 f3 0f 1e fa b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 e9 83 0d 00 f7 d8 [ 5.267787] RSP: 002b:00007ffd7c4c9468 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 [ 5.267796] RAX: 0000000000000000 RBX: 00005a61592a8b00 RCX: 00007aaa8b32a9fb [ 5.267802] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00005a61592b2080 [ 5.267806] RBP: 00007ffd7c4c9540 R08: 00007aaa8b403b20 R09: 0000000000000020 [ 5.267812] R10: 0000000000000001 R11: 0000000000000246 R12: 00005a61592a8c00 [ 5.267817] R13: 0000000000000000 R14: 00005a61592b2080 R15: 00005a61592a8f10 [ 5.267849] </TASK> [ 5.267854] irq event stamp: 4721 [ 5.267859] hardirqs last enabled at (4727): [<ffffffff814abf50>] __up_console_sem+0x90/0xa0 [ 5.267873] hardirqs last disabled at (4732): [<ffffffff814abf35>] __up_console_sem+0x75/0xa0 [ 5.267884] softirqs last enabled at (3044): [<ffffffff8132adb3>] kernel_fpu_end+0x53/0x70 [ 5.267895] softirqs last disabled at (3042): [<ffffffff8132b5f4>] kernel_fpu_begin_mask+0xc4/0x120 [ 5.267905] ---[ end trace 0000000000000000 ]--- Fixes: bde708f ("fs/dax: always remove DAX page-cache entries when breaking layouts") Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com> Reviewed-by: Friendy Su <friendy.su@sony.com> Reviewed-by: Daniel Palmer <daniel.palmer@sony.com> Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
micromaomao
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Oct 11, 2025
net/bridge/br_private.h:1627 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
7 locks held by socat/410:
#0: ffff88800d7a9c90 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_stream_connect+0x43/0xa0
#1: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: __ip_queue_xmit+0x62/0x1830
[..]
#6: ffffffff9a779900 (rcu_read_lock){....}-{1:3}, at: nf_hook.constprop.0+0x8a/0x440
Call Trace:
lockdep_rcu_suspicious.cold+0x4f/0xb1
br_vlan_fill_forward_path_pvid+0x32c/0x410 [bridge]
br_fill_forward_path+0x7a/0x4d0 [bridge]
Use to correct helper, non _rcu variant requires RTNL mutex.
Fixes: bcf2766 ("net: bridge: resolve forwarding path for VLAN tag actions in bridge devices")
Signed-off-by: Eric Woudstra <ericwouds@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
micromaomao
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Dec 20, 2025
When interrupting perf stat in repeat mode with a signal the signal is passed to the child process but the repeat doesn't terminate: ``` $ perf stat -v --null --repeat 10 sleep 1 Control descriptor is not initialized [ perf stat: executing run #1 ... ] [ perf stat: executing run #2 ... ] ^Csleep: Interrupt [ perf stat: executing run #3 ... ] [ perf stat: executing run #4 ... ] [ perf stat: executing run #5 ... ] [ perf stat: executing run #6 ... ] [ perf stat: executing run #7 ... ] [ perf stat: executing run #8 ... ] [ perf stat: executing run #9 ... ] [ perf stat: executing run #10 ... ] Performance counter stats for 'sleep 1' (10 runs): 0.9500 +- 0.0512 seconds time elapsed ( +- 5.39% ) 0.01user 0.02system 0:09.53elapsed 0%CPU (0avgtext+0avgdata 18940maxresident)k 29944inputs+0outputs (0major+2629minor)pagefaults 0swaps ``` Terminate the repeated run and give a reasonable exit value: ``` $ perf stat -v --null --repeat 10 sleep 1 Control descriptor is not initialized [ perf stat: executing run #1 ... ] [ perf stat: executing run #2 ... ] [ perf stat: executing run #3 ... ] ^Csleep: Interrupt Performance counter stats for 'sleep 1' (10 runs): 0.680 +- 0.321 seconds time elapsed ( +- 47.16% ) Command exited with non-zero status 130 0.00user 0.01system 0:02.05elapsed 0%CPU (0avgtext+0avgdata 70688maxresident)k 0inputs+0outputs (0major+5002minor)pagefaults 0swaps ``` Note, this also changes the exit value for non-repeat runs when interrupted by a signal. Reported-by: Ingo Molnar <mingo@kernel.org> Closes: https://lore.kernel.org/lkml/aS5wjmbAM9ka3M2g@gmail.com/ Signed-off-by: Ian Rogers <irogers@google.com> Tested-by: Thomas Richter <tmricht@linux.ibm.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
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Correctness TBD...