Introduces 3 new crash types to LKDTM to reproduce deadlock patterns involving folio_lock(), which operates on a wait-on-bit mechanism. 1. FOLIO_LOCK_AA: Triggers a self-deadlock (AA) by attempting to acquire the same folio lock twice in the same execution context. 2. FOLIO_LOCK_ABBA: Triggers a classic ABBA deadlock between two threads trying to folio lock two different folios in reverse order. 3. FOLIO_MUTEX_LOCK_ABBA: Reproduces an ABBA deadlock involving a folio_lock() and a mutex. This verifies lockdep's ability to track dependencies between sleeping locks (wait-on-bit) and mutexes. These tests allow developers to validate the kernel's behavior (e.g., hung task detection enabled, DEPT reporting[1][2]) under wait/event-based deadlock conditions. [1] https://lwn.net/Articles/1036222/ [2] https://lore.kernel.org/lkml/20251205071855.72743-1-byungchul@sk.com/ (1) LOCKDEP & DETECT_HUNG_TASK enabled kernel log: Lockdep does not detect these issues because it requires the lock and unlock to happen within the same execution context. However, it also fails to detect AA deadlocks involving folio_lock even when they occur within the same execution context. Consequently, all three of these cases are only detected as hung tasks. # echo FOLIO_LOCK_AA > /sys/kernel/debug/provoke-crash/DIRECT [ 20.428887] lkdtm: Performing direct entry FOLIO_LOCK_AA [ 29.579353] hrtimer: interrupt took 32992 ns [ 60.613392] INFO: task bash:923 blocked for more than 30 seconds. [ 60.613708] Not tainted 6.19.0-virtme #30 [ 60.613868] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 60.614006] task:bash state:D stack:12600 pid:923 tgid:923 ppid:915 task_flags:0x400100 flags:0x00080000 [ 60.614190] Call Trace: [ 60.614256] [ 60.614304] __schedule+0x5e7/0x1170 [ 60.614377] schedule+0x3a/0x130 [ 60.614437] io_schedule+0x46/0x70 [ 60.614503] folio_wait_bit_common+0x125/0x2d0 [ 60.614590] ? __pfx_wake_page_function+0x10/0x10 [ 60.614673] lkdtm_FOLIO_LOCK_AA+0x8a/0x90 [ 60.614732] lkdtm_do_action+0x18/0x30 [ 60.614793] direct_entry+0x8d/0xe0 [ 60.614859] full_proxy_write+0x69/0xa0 [ 60.614926] vfs_write+0xdf/0x570 [ 60.614990] ? srso_alias_return_thunk+0x5/0xfbef5 [ 60.615087] ? find_held_lock+0x2b/0x80 [ 60.615154] ? exc_page_fault+0x82/0x1d0 [ 60.615218] ? srso_alias_return_thunk+0x5/0xfbef5 [ 60.615310] ? lock_release+0xcd/0x270 [ 60.615366] ? handle_mm_fault+0xde/0x220 [ 60.615436] ksys_write+0x73/0xf0 [ 60.615501] do_syscall_64+0xbd/0xf80 [ 60.615688] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 60.616034] RIP: 0033:0x7f35aa463340 [ 60.616334] RSP: 002b:00007ffe24f07ba8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 [ 60.616863] RAX: ffffffffffffffda RBX: 000000000000000e RCX: 00007f35aa463340 [ 60.617357] RDX: 000000000000000e RSI: 000056539115fed0 RDI: 0000000000000001 [ 60.618120] RBP: 000056539115fed0 R08: 0000000000000007 R09: 0000000000000073 [ 60.618302] R10: 0000000000001000 R11: 0000000000000202 R12: 000000000000000e [ 60.618422] R13: 00007f35aa53f760 R14: 000000000000000e R15: 00007f35aa53a9e0 [ 60.618544] [ 60.618591] [ 60.618591] Showing all locks held in the system: [ 60.618704] 1 lock held by khungtaskd/116: [ 60.618767] #0: ffffffff89d6d760 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 [ 60.618910] 1 lock held by bash/923: [ 60.618969] #0: ffff8daa81c983f0 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x73/0xf0 [ 60.619087] [ 60.619121] ============================================= [ 60.619121] [ 90.821362] INFO: task bash:923 blocked for more than 60 seconds. [ 90.821604] Not tainted 6.19.0-virtme #30 [ 90.821711] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 90.821882] task:bash state:D stack:12600 pid:923 tgid:923 ppid:915 task_flags:0x400100 flags:0x00080000 [ 90.822091] Call Trace: [ 90.822156] [ 90.822229] __schedule+0x5e7/0x1170 [ 90.822382] schedule+0x3a/0x130 [ 90.822475] io_schedule+0x46/0x70 [ 90.822562] folio_wait_bit_common+0x125/0x2d0 [ 90.822687] ? __pfx_wake_page_function+0x10/0x10 [ 90.822809] lkdtm_FOLIO_LOCK_AA+0x8a/0x90 [ 90.822902] lkdtm_do_action+0x18/0x30 [ 90.822986] direct_entry+0x8d/0xe0 [ 90.823078] full_proxy_write+0x69/0xa0 [ 90.823176] vfs_write+0xdf/0x570 [ 90.823284] ? srso_alias_return_thunk+0x5/0xfbef5 [ 90.823397] ? find_held_lock+0x2b/0x80 [ 90.823486] ? exc_page_fault+0x82/0x1d0 [ 90.823570] ? srso_alias_return_thunk+0x5/0xfbef5 [ 90.823677] ? lock_release+0xcd/0x270 [ 90.823762] ? handle_mm_fault+0xde/0x220 [ 90.823859] ksys_write+0x73/0xf0 [ 90.823954] do_syscall_64+0xbd/0xf80 [ 90.824075] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 90.824189] RIP: 0033:0x7f35aa463340 [ 90.824290] RSP: 002b:00007ffe24f07ba8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 [ 90.824449] RAX: ffffffffffffffda RBX: 000000000000000e RCX: 00007f35aa463340 [ 90.824602] RDX: 000000000000000e RSI: 000056539115fed0 RDI: 0000000000000001 [ 90.824755] RBP: 000056539115fed0 R08: 0000000000000007 R09: 0000000000000073 [ 90.824910] R10: 0000000000001000 R11: 0000000000000202 R12: 000000000000000e [ 90.825063] R13: 00007f35aa53f760 R14: 000000000000000e R15: 00007f35aa53a9e0 [ 90.825270] [ 90.825320] [ 90.825320] Showing all locks held in the system: [ 90.825405] 1 lock held by khungtaskd/116: [ 90.825453] #0: ffffffff89d6d760 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 [ 90.825577] 1 lock held by bash/923: [ 90.825624] #0: ffff8daa81c983f0 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x73/0xf0 [ 90.825730] [ 90.825762] ============================================= # echo FOLIO_LOCK_ABBA > /sys/kernel/debug/provoke-crash/DIRECT [ 12.625758] lkdtm: Performing direct entry FOLIO_LOCK_ABBA [ 60.622597] INFO: task lkdtm_folio_A:923 blocked for more than 30 seconds. [ 60.623573] Not tainted 6.19.0-virtme #30 [ 60.624034] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 60.624624] task:lkdtm_folio_A state:D stack:15288 pid:923 tgid:923 ppid:2 task_flags:0x208040 flags:0x00080000 [ 60.624832] Call Trace: [ 60.624878] [ 60.624931] __schedule+0x5e7/0x1170 [ 60.625020] schedule+0x3a/0x130 [ 60.625089] io_schedule+0x46/0x70 [ 60.625173] folio_wait_bit_common+0x125/0x2d0 [ 60.625267] ? __pfx_wake_page_function+0x10/0x10 [ 60.625358] ? __pfx_lkdtm_folio_AB_kthread+0x10/0x10 [ 60.625424] lkdtm_folio_AB_kthread+0x54/0x60 [ 60.625490] kthread+0xfe/0x200 [ 60.625544] ? __pfx_kthread+0x10/0x10 [ 60.625599] ret_from_fork+0x2b2/0x2e0 [ 60.625650] ? __pfx_kthread+0x10/0x10 [ 60.625716] ret_from_fork_asm+0x1a/0x30 [ 60.625794] [ 60.625829] INFO: task lkdtm_folio_B:924 blocked for more than 30 seconds. [ 60.625904] Not tainted 6.19.0-virtme #30 [ 60.625964] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 60.626049] task:lkdtm_folio_B state:D stack:15288 pid:924 tgid:924 ppid:2 task_flags:0x208040 flags:0x00080000 [ 60.626186] Call Trace: [ 60.626219] [ 60.626259] __schedule+0x5e7/0x1170 [ 60.626326] schedule+0x3a/0x130 [ 60.626377] io_schedule+0x46/0x70 [ 60.626429] folio_wait_bit_common+0x125/0x2d0 [ 60.626501] ? __pfx_wake_page_function+0x10/0x10 [ 60.626570] ? __pfx_lkdtm_folio_BA_kthread+0x10/0x10 [ 60.626634] lkdtm_folio_BA_kthread+0x5e/0x60 [ 60.626698] kthread+0xfe/0x200 [ 60.626749] ? __pfx_kthread+0x10/0x10 [ 60.626807] ret_from_fork+0x2b2/0x2e0 [ 60.626860] ? __pfx_kthread+0x10/0x10 [ 60.626913] ret_from_fork_asm+0x1a/0x30 [ 60.626992] [ 60.627027] [ 60.627027] Showing all locks held in the system: [ 60.627133] 1 lock held by khungtaskd/116: [ 60.627183] #0: ffffffffa816d760 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 [ 60.627310] [ 60.627344] ============================================= # echo FOLIO_MUTEX_LOCK_ABBA > /sys/kernel/debug/provoke-crash/DIRECT [ 60.096166] lkdtm: Performing direct entry FOLIO_MUTEX_LOCK_ABBA [ 90.808780] INFO: task lkdtm_folio_mut:925 blocked for more than 30 seconds. [ 90.809074] Not tainted 6.19.0-virtme #30 [ 90.809182] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 90.809293] task:lkdtm_folio_mut state:D stack:14864 pid:925 tgid:925 ppid:2 task_flags:0x208040 flags:0x00080000 [ 90.809453] Call Trace: [ 90.809497] [ 90.809606] __schedule+0x5e7/0x1170 [ 90.809686] schedule+0x3a/0x130 [ 90.809748] io_schedule+0x46/0x70 [ 90.809800] folio_wait_bit_common+0x125/0x2d0 [ 90.809874] ? __pfx_wake_page_function+0x10/0x10 [ 90.809944] ? __pfx_lkdtm_folio_mutex_kthread+0x10/0x10 [ 90.810010] lkdtm_folio_mutex_kthread+0x4e/0x50 [ 90.810074] kthread+0xfe/0x200 [ 90.810128] ? __pfx_kthread+0x10/0x10 [ 90.810183] ret_from_fork+0x2b2/0x2e0 [ 90.810232] ? __pfx_kthread+0x10/0x10 [ 90.810283] ret_from_fork_asm+0x1a/0x30 [ 90.810361] [ 90.810395] INFO: task lkdtm_mutex_fol:926 blocked for more than 30 seconds. [ 90.810481] Not tainted 6.19.0-virtme #30 [ 90.810558] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 90.810645] task:lkdtm_mutex_fol state:D stack:14840 pid:926 tgid:926 ppid:2 task_flags:0x208040 flags:0x00080000 [ 90.810765] Call Trace: [ 90.810798] [ 90.810839] __schedule+0x5e7/0x1170 [ 90.810909] schedule+0x3a/0x130 [ 90.810961] io_schedule+0x46/0x70 [ 90.811014] folio_wait_bit_common+0x125/0x2d0 [ 90.811087] ? __pfx_wake_page_function+0x10/0x10 [ 90.811156] ? __pfx_lkdtm_mutex_folio_kthread+0x10/0x10 [ 90.811221] lkdtm_mutex_folio_kthread+0x4e/0x50 [ 90.811286] kthread+0xfe/0x200 [ 90.811339] ? __pfx_kthread+0x10/0x10 [ 90.811395] ret_from_fork+0x2b2/0x2e0 [ 90.811444] ? __pfx_kthread+0x10/0x10 [ 90.811496] ret_from_fork_asm+0x1a/0x30 [ 90.811587] [ 90.811622] [ 90.811622] Showing all locks held in the system: [ 90.811704] 1 lock held by khungtaskd/116: [ 90.811752] #0: ffffffff8556d760 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 [ 90.811876] 1 lock held by lkdtm_mutex_fol/926: [ 90.811937] #0: ffffffff856229a8 (mutex_b){+.+.}-{4:4}, at: lkdtm_mutex_folio_kthread+0x32/0x50 [ 90.812086] [ 90.812120] ============================================= (2) DEPT & DETECT_HUNG_TASK enabled kernel log: Currently, DEPT lacks the capability to detect FOLIO_LOCK_AA; however, it is capable of detecting FOLIO_LOCK_ABBA and FOLIO_MUTEX_LOCK_ABBA. # echo FOLIO_LOCK_AA > /sys/kernel/debug/provoke-crash/DIRECT [ 58.674392] lkdtm: Performing direct entry FOLIO_LOCK_AA [ 91.323323] INFO: task bash:926 blocked for more than 30 seconds. [ 91.323768] Not tainted 6.19.0-virtme #29 [ 91.324148] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 91.324536] task:bash state:D stack:12536 pid:926 tgid:926 ppid:918 task_flags:0x400100 flags:0x00080000 [ 91.325116] Call Trace: [ 91.325284] [ 91.325444] ? __schedule+0x5e9/0x11b0 [ 91.325661] __schedule+0x61c/0x11b0 [ 91.325886] schedule+0x3a/0x130 [ 91.326282] io_schedule+0x46/0x70 [ 91.326501] folio_wait_bit_common+0x1ab/0x440 [ 91.326776] ? __pfx_wake_page_function+0x10/0x10 [ 91.327141] lkdtm_FOLIO_LOCK_AA+0x10c/0x1b0 [ 91.327397] lkdtm_do_action+0x18/0x30 [ 91.327596] direct_entry+0x8d/0xe0 [ 91.327799] full_proxy_write+0x69/0xa0 [ 91.328116] vfs_write+0xea/0x600 [ 91.328325] ? srso_alias_return_thunk+0x5/0xfbef5 [ 91.328571] ? find_held_lock+0x2b/0x80 [ 91.328768] ? srso_alias_return_thunk+0x5/0xfbef5 [ 91.329104] ? srso_alias_return_thunk+0x5/0xfbef5 [ 91.329343] ? from_pool+0x7d/0x190 [ 91.329541] ? srso_alias_return_thunk+0x5/0xfbef5 [ 91.329781] ? dept_enter+0x68/0xa0 [ 91.330082] ksys_write+0x76/0xf0 [ 91.330285] do_syscall_64+0xc2/0xf80 [ 91.330485] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 91.330721] RIP: 0033:0x7f462490c340 [ 91.331038] RSP: 002b:00007ffe8c0b03c8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 [ 91.331405] RAX: ffffffffffffffda RBX: 000000000000000e RCX: 00007f462490c340 [ 91.331743] RDX: 000000000000000e RSI: 00005595da40fed0 RDI: 0000000000000001 [ 91.332182] RBP: 00005595da40fed0 R08: 0000000000000007 R09: 0000000000000073 [ 91.332522] R10: 0000000000001000 R11: 0000000000000202 R12: 000000000000000e [ 91.332862] R13: 00007f46249e8760 R14: 000000000000000e R15: 00007f46249e39e0 [ 91.333330] [ 91.333480] [ 91.333480] Showing all locks held in the system: [ 91.333772] 1 lock held by khungtaskd/116: [ 91.334083] #0: ffffffff82b80620 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 [ 91.334618] 1 lock held by bash/926: [ 91.334814] #0: ffff8be901beb570 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x76/0xf0 [ 91.335471] [ 91.335622] ============================================= Currently, DEPT misidentifies FOLIO_LOCK_ABBA as an AA deadlock. DEPT needs to be refined to correctly distinguish between separate folio locks. # echo FOLIO_LOCK_ABBA > /sys/kernel/debug/provoke-crash/DIRECT [ 24.856137] lkdtm: Performing direct entry FOLIO_LOCK_ABBA [ 24.859449] =================================================== [ 24.859709] DEPT: Circular dependency has been detected. [ 24.859845] 6.19.0-virtme #29 Not tainted [ 24.859948] --------------------------------------------------- [ 24.860106] summary [ 24.860184] --------------------------------------------------- [ 24.860343] *** AA DEADLOCK *** [ 24.860343] [ 24.860475] context A [ 24.860549] [S] (unknown)(pg_locked_map:0) [ 24.860681] [W] dept_page_wait_on_bit(pg_locked_map:0) [ 24.860812] [E] dept_page_clear_bit(pg_locked_map:0) [ 24.860943] [ 24.861021] [S]: start of the event context [ 24.861126] [W]: the wait blocked [ 24.861243] [E]: the event not reachable [ 24.861333] --------------------------------------------------- [ 24.861484] context A's detail [ 24.861578] --------------------------------------------------- [ 24.861702] context A [ 24.861770] [S] (unknown)(pg_locked_map:0) [ 24.861887] [W] dept_page_wait_on_bit(pg_locked_map:0) [ 24.862005] [E] dept_page_clear_bit(pg_locked_map:0) [ 24.862123] [ 24.862172] [S] (unknown)(pg_locked_map:0): [ 24.862265] (N/A) [ 24.862333] [ 24.862382] [W] dept_page_wait_on_bit(pg_locked_map:0): [ 24.862501] [] kthread+0xfe/0x200 [ 24.862618] stacktrace: [ 24.862686] kthread+0xfe/0x200 [ 24.862778] ret_from_fork+0x29d/0x2e0 [ 24.862871] ret_from_fork_asm+0x1a/0x30 [ 24.862985] [ 24.863049] [E] dept_page_clear_bit(pg_locked_map:0): [ 24.863158] [] lkdtm_folio_AB_kthread+0xaa/0x190 [ 24.863301] stacktrace: [ 24.863369] lkdtm_folio_AB_kthread+0xaa/0x190 [ 24.863487] kthread+0xfe/0x200 [ 24.863576] ret_from_fork+0x29d/0x2e0 [ 24.863661] ret_from_fork_asm+0x1a/0x30 [ 24.863767] --------------------------------------------------- [ 24.863898] information that might be helpful [ 24.864008] --------------------------------------------------- [ 24.864139] CPU: 2 UID: 0 PID: 928 Comm: lkdtm_folio_A Not tainted 6.19.0-virtme #29 PREEMPT(full) [ 24.864145] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 [ 24.864147] C?all Trace: [ 24.864150] 0 [ 24.864153] dump_stack_lvl+0x69/0xa0 [ 24.864162] cb_check_dl+0x6be/0x760 [ 24.864173] ? srso_alias_return_thunk+0x5/0xfbef5 [ 24.864178] ? lock_acquire+0x26b/0x2b0 [ 24.864188] rbfs+0x138/0x1c0 [ 24.864192] t? srso_alias_ret@urn_thunk+0x5/0xvfbef5 [ 24.864203] tadd_dep+0xd6/0x1mc0 [ 24.864209] n? srso_alias_retgurn_thunk+0x5/0x:fbef5 [ 24.864212] h? __pfx_bfs_inito_check_dl+0x10/0mex10 [ 24.864217] i? __pfx_bfs_extemnd_dep+0x10/0x10/ [ 24.864221] a? __pfx_bfs_dequgeue_dep+0x10/0x1in0 [ 24.864225] ? __pfx_cb_check#_dl+0x10/0x10 [ 24.864233] __dept_event+0x489/0x520 [ 24.864241] ? srso_alias_return_thunk+0x5/0xfbef5 [ 24.864246] ? lkdtm_folio_AB_kthread+0xaa/0x190 [ 24.864252] dept_event+0x99/0xc0 [ 24.864262] ? __pfx_lkdtm_folio_AB_kthread+0x10/0x10 [ 24.864267] folio_unlock+0x3c/0x60 [ 24.864273] lkdtm_folio_AB_kthread+0xaa/0x190 [ 24.864279] kthread+0xfe/0x200 [ 24.864285] ? __pfx_kthread+0x10/0x10 [ 24.864293] ret_from_fork+0x29d/0x2e0 [ 24.864297] ? __pfx_kthread+0x10/0x10 [ 24.864302] ret_from_fork_asm+0x1a/0x30 [ 24.864324] # echo FOLIO_MUTEX_LOCK_ABBA > /sys/kernel/debug/provoke-crash/DIRECT [ 23.480083] lkdtm: Performing direct entry FOLIO_MUTEX_LOCK_ABBA [ 23.483404] =================================================== [ 23.483623] DEPT: Circular dependency has been detected. [ 23.483755] 6.19.0-virtme #29 Not tainted [ 23.483884] --------------------------------------------------- [ 23.484042] summary [ 23.484155] --------------------------------------------------- [** DEADLOCK *** [ 23.484343] [ 23.484635] context A [ 23.484766] [S] lock(mutex_b:0) [ 23.484953] [W] dept_page_wait_on_bit(pg_locked_map:0) [ 23.485087] [E] unlock(mutex_b:0) [ 23.485198] [ 23.485277] context B [ 23.485351] [S] (unknown)(pg_locked_map:0)r [ 23.485550] [W] lock(mutext_b:0) [ 23.486150] [E] dept_page_iclear_bit(pg_locrked_map:0) [ 23.486964] [ 23.487371] [S]: start of then event context [ 23.487988] [W]: the wait blo/cked [ 23.488543] [E]: the event not reachable [ 23.488652] ------------------------------------------------------ [ 23.488987] ckontext A's detail [ 23.489171] ----------------------------------------------------- [ 23.489468] context A [ 23.489571] [S] lock(mutex_b:0) [ 23.489737] [W] dept_page_wait_on_bit(pg_lnocked_map:0) [ 23.489997] [E] unlock(mutex_b:0) [ 23.490138] [ 23.490232] [S] lock(mutex_b:0): [ 23.490349] [] lkdtm_mutex_folio_kthread+0x40/0xe0 [ 23.490500] stacktrace: [ 23.490557] lkdtm_mutex_folio_kthread+0x40/0xe0 [ 23.490662] kthread+0xfe/0x200 [ 23.490742] ret_from_fork+0x29d/0x2e0 [ 23.490821] ret_from_fork_asm+0x1a/0x30 [ 23.490926] [ 23.490987] [W] dept_page_wait_on_bit(pg_locked_map:0): [ 23.491090] [] kthread+0xfe/0x200 [ 23.491199] stacktrace: [ 23.491263] kthread+0xfe/0x200 [ 23.491347] ret_from_fork+0x29d/0x2e0 [ 23.491431] ret_from_fork_asm+0x1a/0x30 [ 23.491537] [ 23.491601] [E] unlock(mutex_b:0): [ 23.491684] (N/A) [ 23.491754] --------------------------------------------------- [ 23.491908] context B's detail [ 23.491992] --------------------------------------------------- [ 23.492118] context B [ 23.492175] [S] (unknown)(pg_locked_map:0) [ 23.492277] [W] lock(mutex_b:0) [ 23.492358] [E] dept_page_clear_bit(pg_locked_map:0) [ 23.492459] [ 23.492523] [S] (unknown)(pg_locked_map:0): [ 23.492603] (N/A) [ 23.492664] [ 23.492722] [W] lock(mutex_b:0): [ 23.492807] [] lkdtm_folio_mutex_kthread+0x28/0xe0 [ 23.492947] stacktrace: [ 23.493006] lkdtm_folio_mutex_kthread+0x28/0xe0 [ 23.493115] kthread+0xfe/0x200 [ 23.493197] ret_from_fork+0x29d/0x2e0 [ 23.493280] ret_from_fork_asm+0x1a/0x30 [ 23.493382] [ 23.493446] [E] dept_page_clear_bit(pg_locked_map:0): [ 23.493550] [] lkdtm_folio_mutex_kthread+0x40/0xe0 [ 23.493680] stacktrace: [ 23.493740] lkdtm_folio_mutex_kthread+0x40/0xe0 [ 23.493847] kthread+0xfe/0x200 [ 23.493933] ret_from_fork+0x29d/0x2e0 [ 23.494015] ret_from_fork_asm+0x1a/0x30 [ 23.494122] --------------------------------------------------- [ 23.494241] information that might be helpful [ 23.494348] --------------------------------------------------- [ 23.494479] CPU: 3 UID: 0 PID: 928 Comm: lkdtm_mutex_fol Not tainted 6.19.0-virtme #29 PREEMPT(full) [ 23.494485] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 [ 23.494487] Call Trace: [ 23.494491] [ 23.494495] dump_stack_lvl+0x69/0xa0 [ 23.494502] cb_check_dl+0x6be/0x760 [ 23.494517] bfs+0x17d/0x1c0 [ 23.494521] ? srso_alias_return_thunk+0x5/0xfbef5 [ 23.494530] add_dep+0xd6/0x1c0 [ 23.494534] ? lkdtm_mutex_folio_kthread+0x40/0xe0 [ 23.494538] ? __pfx_bfs_init_check_dl+0x10/0x10 [ 23.494541] ? __pfx_bfs_extend_dep+0x10/0x10 [ 23.494544] ? __pfx_bfs_dequeue_dep+0x10/0x10 [ 23.494548] ? __pfx_cb_check_dl+0x10/0x10 [ 23.494555] __dept_wait+0x274/0x6a0 [ 23.494561] ? kthread+0xfe/0x200 [ 23.494566] ? __mutex_lock+0xae3/0x1230 [ 23.494572] ? srso_alias_return_thunk+0x5/0xfbef5 [ 23.494575] ? dept_enter+0x68/0xa0 [ 23.494582] ? kthread+0xfe/0x200 [ 23.494587] dept_wait+0xa7/0xc0 [ 23.494595] ? __pfx_lkdtm_mutex_folio_kthread+0x10/0x10 [ 23.494600] lkdtm_mutex_folio_kthread+0x9d/0xe0 [ 23.494604] kthread+0xfe/0x200 [ 23.494609] ? __pfx_kthread+0x10/0x10 [ 23.494616] ret_from_fork+0x29d/0x2e0 [ 23.494619] ? __pfx_kthread+0x10/0x10 [ 23.494623] ret_from_fork_asm+0x1a/0x30 [ 23.494641] Cc: Byungchul Park Cc: Yeoreum Yun Assisted-by: Gemini:gemini-3.1-pro Signed-off-by: Yunseong Kim --- drivers/misc/lkdtm/Makefile | 1 + drivers/misc/lkdtm/bugs.c | 1 + drivers/misc/lkdtm/core.c | 1 + drivers/misc/lkdtm/deadlock.c | 149 ++++++++++++++++++++++++ drivers/misc/lkdtm/lkdtm.h | 1 + tools/testing/selftests/lkdtm/tests.txt | 3 + 6 files changed, 156 insertions(+) create mode 100644 drivers/misc/lkdtm/deadlock.c diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile index 03ebe33185f9..02264813a346 100644 --- a/drivers/misc/lkdtm/Makefile +++ b/drivers/misc/lkdtm/Makefile @@ -3,6 +3,7 @@ obj-$(CONFIG_LKDTM) += lkdtm.o lkdtm-$(CONFIG_LKDTM) += core.o lkdtm-$(CONFIG_LKDTM) += bugs.o +lkdtm-$(CONFIG_LKDTM) += deadlock.o lkdtm-$(CONFIG_LKDTM) += heap.o lkdtm-$(CONFIG_LKDTM) += perms.o lkdtm-$(CONFIG_LKDTM) += refcount.o diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index 376047beea3d..193b284bcebd 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -694,6 +694,7 @@ static noinline void lkdtm_CORRUPT_PAC(void) } static struct crashtype crashtypes[] = { + CRASHTYPE(PANIC), CRASHTYPE(PANIC_STOP_IRQOFF), CRASHTYPE(BUG), diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index 5732fd59a227..ea6201861bb7 100644 --- a/drivers/misc/lkdtm/core.c +++ b/drivers/misc/lkdtm/core.c @@ -89,6 +89,7 @@ static struct crashpoint crashpoints[] = { /* List of possible types for crashes that can be triggered. */ static const struct crashtype_category *crashtype_categories[] = { &bugs_crashtypes, + &deadlock_crashtypes, &heap_crashtypes, &perms_crashtypes, &refcount_crashtypes, diff --git a/drivers/misc/lkdtm/deadlock.c b/drivers/misc/lkdtm/deadlock.c new file mode 100644 index 000000000000..d244767e3ebc --- /dev/null +++ b/drivers/misc/lkdtm/deadlock.c @@ -0,0 +1,149 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * This is for all the tests related to deadlock. + */ +#include "lkdtm.h" +#include +#include +#include +#include +#include +#include +#include + +static struct folio *folio_A; +static struct folio *folio_B; + +/* + * Triggering a simple AA deadlock on a folio, Attempting to acquire the same + * folio twice in the same execution context, resulting in a self-deadlock. + */ +static void lkdtm_FOLIO_LOCK_AA(void) +{ + folio_A = folio_alloc(GFP_KERNEL | __GFP_ZERO, 0); + + if (!folio_A) { + pr_err("folio_alloc() failed.\n"); + return; + } + + folio_lock(folio_A); + folio_lock(folio_A); + + /* Unreachable */ + folio_unlock(folio_A); + + folio_put(folio_A); +} + +/* + * Attempting the 'AB' order for ABBA deadlock + */ +static int lkdtm_folio_AB_kthread(void *data) +{ + while (true) { + folio_lock(folio_A); + folio_lock(folio_B); + folio_unlock(folio_B); + folio_unlock(folio_A); + } + + return 0; +} + +/* + * Attempting the 'BA' order for ABBA deadlock + */ +static int lkdtm_folio_BA_kthread(void *data) +{ + while (true) { + folio_lock(folio_B); + folio_lock(folio_A); + folio_unlock(folio_A); + folio_unlock(folio_B); + } + + return 0; +} + +/* + * Spawning kthreads that attempt to acquire Waiter A and Waiter B in reverse + * order. Leading to a state where Thread A holds Waiter A and waits for + * Waiter B, while Thread B holds Waiter B and waits for Waiter A. + */ +static void lkdtm_FOLIO_LOCK_ABBA(void) +{ + struct task_struct *t0, *t1; + + folio_A = folio_alloc(GFP_KERNEL | __GFP_ZERO, 0); + folio_B = folio_alloc(GFP_KERNEL | __GFP_ZERO, 0); + + if (!folio_A || !folio_B) { + pr_err("folio_alloc() failed.\n"); + return; + } + + t0 = kthread_run(lkdtm_folio_AB_kthread, NULL, "lkdtm_folio_A"); + t1 = kthread_run(lkdtm_folio_BA_kthread, NULL, "lkdtm_folio_B"); + + if (IS_ERR(t0) || IS_ERR(t1)) + pr_err("failed to start kthread.\n"); + + folio_put(folio_A); + folio_put(folio_B); +} + +DEFINE_MUTEX(mutex_b); + +/* Attempting 'folio_lock() A then Mutex B' order */ +static int lkdtm_folio_mutex_kthread(void *data) +{ + while (true) { + folio_lock(folio_A); + mutex_lock(&mutex_b); + mutex_unlock(&mutex_b); + folio_unlock(folio_A); + } + + return 0; +} + +/* Attempting 'Mutex B then folio_lock() A' order */ +static int lkdtm_mutex_folio_kthread(void *data) +{ + while (true) { + mutex_lock(&mutex_b); + folio_lock(folio_A); + folio_unlock(folio_A); + mutex_unlock(&mutex_b); + } + + return 0; +} + +/* Triggering ABBA deadlock between folio_lock() and mutex. */ +static void lkdtm_FOLIO_MUTEX_LOCK_ABBA(void) +{ + struct task_struct *t0, *t1; + + folio_A = folio_alloc(GFP_KERNEL | __GFP_ZERO, 0); + + t0 = kthread_run(lkdtm_folio_mutex_kthread, NULL, "lkdtm_folio_mutex"); + t1 = kthread_run(lkdtm_mutex_folio_kthread, NULL, "lkdtm_mutex_folio"); + + if (IS_ERR(t0) || IS_ERR(t1)) + pr_err("failed to start kthreads\n"); + + folio_put(folio_A); +} + +static struct crashtype crashtypes[] = { + CRASHTYPE(FOLIO_LOCK_AA), + CRASHTYPE(FOLIO_LOCK_ABBA), + CRASHTYPE(FOLIO_MUTEX_LOCK_ABBA), +}; + +struct crashtype_category deadlock_crashtypes = { + .crashtypes = crashtypes, + .len = ARRAY_SIZE(crashtypes), +}; diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index 015e0484026b..95898de29c57 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -77,6 +77,7 @@ struct crashtype_category { /* Each category's crashtypes list. */ extern struct crashtype_category bugs_crashtypes; +extern struct crashtype_category deadlock_crashtypes; extern struct crashtype_category heap_crashtypes; extern struct crashtype_category perms_crashtypes; extern struct crashtype_category refcount_crashtypes; diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt index cff124c1eddd..3717942e451e 100644 --- a/tools/testing/selftests/lkdtm/tests.txt +++ b/tools/testing/selftests/lkdtm/tests.txt @@ -83,3 +83,6 @@ FORTIFY_STR_MEMBER detected buffer overflow FORTIFY_MEM_OBJECT detected buffer overflow FORTIFY_MEM_MEMBER detected field-spanning write PPC_SLB_MULTIHIT Recovered +#FOLIO_LOCK_AA Hangs the system +#FOLIO_LOCK_ABBA Hangs the system +#FOLIO_MUTEX_LOCK_ABBA Hangs the system -- 2.53.0