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HID driver callbacks aren't called anymore once hid_destroy_device() has been called. Hence, hid driver_data should be freed only after the hid_destroy_device() function returned as driver_data is used in several callbacks. I observed a crash with kernel 6.10.0 on my T14s Gen 3, after enabling KASAN to debug memory allocation, I got this output: [ 13.050438] ================================================================== [ 13.054060] BUG: KASAN: slab-use-after-free in amd_sfh_get_report+0x3ec/0x530 [amd_sfh] [ 13.054809] psmouse serio1: trackpoint: Synaptics TrackPoint firmware: 0x02, buttons: 3/3 [ 13.056432] Read of size 8 at addr ffff88813152f408 by task (udev-worker)/479 [ 13.060970] CPU: 5 PID: 479 Comm: (udev-worker) Not tainted 6.10.0-arch1-2 #1 893bb55d7f0073f25c46adbb49eb3785fefd74b0 [ 13.063978] Hardware name: LENOVO 21CQCTO1WW/21CQCTO1WW, BIOS R22ET70W (1.40 ) 03/21/2024 [ 13.067860] Call Trace: [ 13.069383] input: TPPS/2 Synaptics TrackPoint as /devices/platform/i8042/serio1/input/input8 [ 13.071486] <TASK> [ 13.071492] dump_stack_lvl+0x5d/0x80 [ 13.074870] snd_hda_intel 0000:33:00.6: enabling device (0000 -> 0002) [ 13.078296] ? amd_sfh_get_report+0x3ec/0x530 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.082199] print_report+0x174/0x505 [ 13.085776] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 13.089367] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.093255] ? amd_sfh_get_report+0x3ec/0x530 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.097464] kasan_report+0xc8/0x150 [ 13.101461] ? amd_sfh_get_report+0x3ec/0x530 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.105802] amd_sfh_get_report+0x3ec/0x530 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.110303] amdtp_hid_request+0xb8/0x110 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.114879] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.119450] sensor_hub_get_feature+0x1d3/0x540 [hid_sensor_hub 3f13be3016ff415bea03008d45d99da837ee3082] [ 13.124097] hid_sensor_parse_common_attributes+0x4d0/0xad0 [hid_sensor_iio_common c3a5cbe93969c28b122609768bbe23efe52eb8f5] [ 13.127404] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.131925] ? __pfx_hid_sensor_parse_common_attributes+0x10/0x10 [hid_sensor_iio_common c3a5cbe93969c28b122609768bbe23efe52eb8f5] [ 13.136455] ? _raw_spin_lock_irqsave+0x96/0xf0 [ 13.140197] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 13.143602] ? devm_iio_device_alloc+0x34/0x50 [industrialio 3d261d5e5765625d2b052be40e526d62b1d2123b] [ 13.147234] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.150446] ? __devm_add_action+0x167/0x1d0 [ 13.155061] hid_gyro_3d_probe+0x120/0x7f0 [hid_sensor_gyro_3d 63da36a143b775846ab2dbb86c343b401b5e3172] [ 13.158581] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.161814] platform_probe+0xa2/0x150 [ 13.165029] really_probe+0x1e3/0x8a0 [ 13.168243] __driver_probe_device+0x18c/0x370 [ 13.171500] driver_probe_device+0x4a/0x120 [ 13.175000] __driver_attach+0x190/0x4a0 [ 13.178521] ? __pfx___driver_attach+0x10/0x10 [ 13.181771] bus_for_each_dev+0x106/0x180 [ 13.185033] ? __pfx__raw_spin_lock+0x10/0x10 [ 13.188229] ? __pfx_bus_for_each_dev+0x10/0x10 [ 13.191446] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.194382] bus_add_driver+0x29e/0x4d0 [ 13.197328] driver_register+0x1a5/0x360 [ 13.200283] ? __pfx_hid_gyro_3d_platform_driver_init+0x10/0x10 [hid_sensor_gyro_3d 63da36a143b775846ab2dbb86c343b401b5e3172] [ 13.203362] do_one_initcall+0xa7/0x380 [ 13.206432] ? __pfx_do_one_initcall+0x10/0x10 [ 13.210175] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.213211] ? kasan_unpoison+0x44/0x70 [ 13.216688] do_init_module+0x238/0x750 [ 13.219696] load_module+0x5011/0x6af0 [ 13.223096] ? kasan_save_stack+0x30/0x50 [ 13.226743] ? kasan_save_track+0x14/0x30 [ 13.230080] ? kasan_save_free_info+0x3b/0x60 [ 13.233323] ? poison_slab_object+0x109/0x180 [ 13.236778] ? __pfx_load_module+0x10/0x10 [ 13.239703] ? poison_slab_object+0x109/0x180 [ 13.243070] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.245924] ? init_module_from_file+0x13d/0x150 [ 13.248745] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.251503] ? init_module_from_file+0xdf/0x150 [ 13.254198] init_module_from_file+0xdf/0x150 [ 13.256826] ? __pfx_init_module_from_file+0x10/0x10 [ 13.259428] ? kasan_save_track+0x14/0x30 [ 13.261959] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.264471] ? kasan_save_free_info+0x3b/0x60 [ 13.267026] ? poison_slab_object+0x109/0x180 [ 13.269494] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.271949] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.274324] ? _raw_spin_lock+0x85/0xe0 [ 13.276671] ? __pfx__raw_spin_lock+0x10/0x10 [ 13.278963] ? __rseq_handle_notify_resume+0x1a6/0xad0 [ 13.281193] idempotent_init_module+0x23b/0x650 [ 13.283420] ? __pfx_idempotent_init_module+0x10/0x10 [ 13.285619] ? __pfx___seccomp_filter+0x10/0x10 [ 13.287714] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.289828] ? __fget_light+0x57/0x420 [ 13.291870] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.293880] ? security_capable+0x74/0xb0 [ 13.295820] __x64_sys_finit_module+0xbe/0x130 [ 13.297874] do_syscall_64+0x82/0x190 [ 13.299898] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.301905] ? irqtime_account_irq+0x3d/0x1f0 [ 13.303877] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.305753] ? __irq_exit_rcu+0x4e/0x130 [ 13.307577] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.309489] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 13.311371] RIP: 0033:0x7a21f96ade9d [ 13.313234] Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 63 de 0c 00 f7 d8 64 89 01 48 [ 13.317051] RSP: 002b:00007ffeae934e78 EFLAGS: 00000246 ORIG_RAX: 0000000000000139 [ 13.319024] RAX: ffffffffffffffda RBX: 00005987276bfcf0 RCX: 00007a21f96ade9d [ 13.321100] RDX: 0000000000000004 RSI: 00007a21f8eda376 RDI: 000000000000001c [ 13.323314] RBP: 00007a21f8eda376 R08: 0000000000000001 R09: 00007ffeae934ec0 [ 13.325505] R10: 0000000000000050 R11: 0000000000000246 R12: 0000000000020000 [ 13.327637] R13: 00005987276c1250 R14: 0000000000000000 R15: 00005987276c4530 [ 13.329737] </TASK> [ 13.333945] Allocated by task 139: [ 13.336111] kasan_save_stack+0x30/0x50 [ 13.336121] kasan_save_track+0x14/0x30 [ 13.336125] __kasan_kmalloc+0xaa/0xb0 [ 13.336129] amdtp_hid_probe+0xb1/0x440 [amd_sfh] [ 13.336138] amd_sfh_hid_client_init+0xb8a/0x10f0 [amd_sfh] [ 13.336144] sfh_init_work+0x47/0x120 [amd_sfh] [ 13.336150] process_one_work+0x673/0xeb0 [ 13.336155] worker_thread+0x795/0x1250 [ 13.336160] kthread+0x290/0x350 [ 13.336164] ret_from_fork+0x34/0x70 [ 13.336169] ret_from_fork_asm+0x1a/0x30 [ 13.338175] Freed by task 139: [ 13.340064] kasan_save_stack+0x30/0x50 [ 13.340072] kasan_save_track+0x14/0x30 [ 13.340076] kasan_save_free_info+0x3b/0x60 [ 13.340081] poison_slab_object+0x109/0x180 [ 13.340085] __kasan_slab_free+0x32/0x50 [ 13.340089] kfree+0xe5/0x310 [ 13.340094] amdtp_hid_remove+0xb2/0x160 [amd_sfh] [ 13.340102] amd_sfh_hid_client_deinit+0x324/0x640 [amd_sfh] [ 13.340107] amd_sfh_hid_client_init+0x94a/0x10f0 [amd_sfh] [ 13.340113] sfh_init_work+0x47/0x120 [amd_sfh] [ 13.340118] process_one_work+0x673/0xeb0 [ 13.340123] worker_thread+0x795/0x1250 [ 13.340127] kthread+0x290/0x350 [ 13.340132] ret_from_fork+0x34/0x70 [ 13.340136] ret_from_fork_asm+0x1a/0x30 [ 13.342482] The buggy address belongs to the object at ffff88813152f400 which belongs to the cache kmalloc-64 of size 64 [ 13.347357] The buggy address is located 8 bytes inside of freed 64-byte region [ffff88813152f400, ffff88813152f440) [ 13.347367] The buggy address belongs to the physical page: [ 13.355409] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x13152f [ 13.355416] anon flags: 0x2ffff8000000000(node=0|zone=2|lastcpupid=0x1ffff) [ 13.355423] page_type: 0xffffefff(slab) [ 13.355429] raw: 02ffff8000000000 ffff8881000428c0 ffffea0004c43a00 0000000000000005 [ 13.355435] raw: 0000000000000000 0000000000200020 00000001ffffefff 0000000000000000 [ 13.355439] page dumped because: kasan: bad access detected [ 13.357295] Memory state around the buggy address: [ 13.357299] ffff88813152f300: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc [ 13.357303] ffff88813152f380: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc [ 13.357306] >ffff88813152f400: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc [ 13.357309] ^ [ 13.357311] ffff88813152f480: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc [ 13.357315] ffff88813152f500: 00 00 00 00 00 00 00 06 fc fc fc fc fc fc fc fc [ 13.357318] ================================================================== [ 13.357405] Disabling lock debugging due to kernel taint [ 13.383534] Oops: general protection fault, probably for non-canonical address 0xe0a1bc4140000013: 0000 [#1] PREEMPT SMP KASAN NOPTI [ 13.383544] KASAN: maybe wild-memory-access in range [0x050e020a00000098-0x050e020a0000009f] [ 13.383551] CPU: 3 PID: 479 Comm: (udev-worker) Tainted: G B 6.10.0-arch1-2 #1 893bb55d7f0073f25c46adbb49eb3785fefd74b0 [ 13.383561] Hardware name: LENOVO 21CQCTO1WW/21CQCTO1WW, BIOS R22ET70W (1.40 ) 03/21/2024 [ 13.383565] RIP: 0010:amd_sfh_get_report+0x81/0x530 [amd_sfh] [ 13.383580] Code: 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 78 03 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 63 08 49 8d 7c 24 10 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 1a 03 00 00 45 8b 74 24 10 45 [ 13.383585] RSP: 0018:ffff8881261f7388 EFLAGS: 00010212 [ 13.383592] RAX: dffffc0000000000 RBX: ffff88813152f400 RCX: 0000000000000002 [ 13.383597] RDX: 00a1c04140000013 RSI: 0000000000000008 RDI: 050e020a0000009b [ 13.383600] RBP: ffff88814d010000 R08: 0000000000000002 R09: fffffbfff3ddb8c0 [ 13.383604] R10: ffffffff9eedc607 R11: ffff88810ce98000 R12: 050e020a0000008b [ 13.383607] R13: ffff88814d010000 R14: dffffc0000000000 R15: 0000000000000004 [ 13.383611] FS: 00007a21f94d0880(0000) GS:ffff8887e7d80000(0000) knlGS:0000000000000000 [ 13.383615] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 13.383618] CR2: 00007e0014c438f0 CR3: 000000012614c000 CR4: 0000000000f50ef0 [ 13.383622] PKRU: 55555554 [ 13.383625] Call Trace: [ 13.383629] <TASK> [ 13.383632] ? __die_body.cold+0x19/0x27 [ 13.383644] ? die_addr+0x46/0x70 [ 13.383652] ? exc_general_protection+0x150/0x240 [ 13.383664] ? asm_exc_general_protection+0x26/0x30 [ 13.383674] ? amd_sfh_get_report+0x81/0x530 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.383686] ? amd_sfh_get_report+0x3ec/0x530 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.383697] amdtp_hid_request+0xb8/0x110 [amd_sfh 05f43221435b5205f734cd9da29399130f398a38] [ 13.383706] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.383713] sensor_hub_get_feature+0x1d3/0x540 [hid_sensor_hub 3f13be3016ff415bea03008d45d99da837ee3082] [ 13.383727] hid_sensor_parse_common_attributes+0x4d0/0xad0 [hid_sensor_iio_common c3a5cbe93969c28b122609768bbe23efe52eb8f5] [ 13.383739] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.383745] ? __pfx_hid_sensor_parse_common_attributes+0x10/0x10 [hid_sensor_iio_common c3a5cbe93969c28b122609768bbe23efe52eb8f5] [ 13.383753] ? _raw_spin_lock_irqsave+0x96/0xf0 [ 13.383762] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 13.383768] ? devm_iio_device_alloc+0x34/0x50 [industrialio 3d261d5e5765625d2b052be40e526d62b1d2123b] [ 13.383790] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.383795] ? __devm_add_action+0x167/0x1d0 [ 13.383806] hid_gyro_3d_probe+0x120/0x7f0 [hid_sensor_gyro_3d 63da36a143b775846ab2dbb86c343b401b5e3172] [ 13.383818] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.383826] platform_probe+0xa2/0x150 [ 13.383832] really_probe+0x1e3/0x8a0 [ 13.383838] __driver_probe_device+0x18c/0x370 [ 13.383844] driver_probe_device+0x4a/0x120 [ 13.383851] __driver_attach+0x190/0x4a0 [ 13.383857] ? __pfx___driver_attach+0x10/0x10 [ 13.383863] bus_for_each_dev+0x106/0x180 [ 13.383868] ? __pfx__raw_spin_lock+0x10/0x10 [ 13.383874] ? __pfx_bus_for_each_dev+0x10/0x10 [ 13.383880] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.383887] bus_add_driver+0x29e/0x4d0 [ 13.383895] driver_register+0x1a5/0x360 [ 13.383902] ? __pfx_hid_gyro_3d_platform_driver_init+0x10/0x10 [hid_sensor_gyro_3d 63da36a143b775846ab2dbb86c343b401b5e3172] [ 13.383910] do_one_initcall+0xa7/0x380 [ 13.383919] ? __pfx_do_one_initcall+0x10/0x10 [ 13.383927] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.383933] ? kasan_unpoison+0x44/0x70 [ 13.383943] do_init_module+0x238/0x750 [ 13.383955] load_module+0x5011/0x6af0 [ 13.383962] ? kasan_save_stack+0x30/0x50 [ 13.383968] ? kasan_save_track+0x14/0x30 [ 13.383973] ? kasan_save_free_info+0x3b/0x60 [ 13.383980] ? poison_slab_object+0x109/0x180 [ 13.383993] ? __pfx_load_module+0x10/0x10 [ 13.384007] ? poison_slab_object+0x109/0x180 [ 13.384012] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384018] ? init_module_from_file+0x13d/0x150 [ 13.384025] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384032] ? init_module_from_file+0xdf/0x150 [ 13.384037] init_module_from_file+0xdf/0x150 [ 13.384044] ? __pfx_init_module_from_file+0x10/0x10 [ 13.384050] ? kasan_save_track+0x14/0x30 [ 13.384055] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384060] ? kasan_save_free_info+0x3b/0x60 [ 13.384066] ? poison_slab_object+0x109/0x180 [ 13.384071] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384080] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384085] ? _raw_spin_lock+0x85/0xe0 [ 13.384091] ? __pfx__raw_spin_lock+0x10/0x10 [ 13.384096] ? __rseq_handle_notify_resume+0x1a6/0xad0 [ 13.384106] idempotent_init_module+0x23b/0x650 [ 13.384114] ? __pfx_idempotent_init_module+0x10/0x10 [ 13.384120] ? __pfx___seccomp_filter+0x10/0x10 [ 13.384129] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384135] ? __fget_light+0x57/0x420 [ 13.384142] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384147] ? security_capable+0x74/0xb0 [ 13.384157] __x64_sys_finit_module+0xbe/0x130 [ 13.384164] do_syscall_64+0x82/0x190 [ 13.384174] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384179] ? irqtime_account_irq+0x3d/0x1f0 [ 13.384188] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384193] ? __irq_exit_rcu+0x4e/0x130 [ 13.384201] ? srso_alias_return_thunk+0x5/0xfbef5 [ 13.384206] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 13.384212] RIP: 0033:0x7a21f96ade9d [ 13.384263] Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 63 de 0c 00 f7 d8 64 89 01 48 [ 13.384267] RSP: 002b:00007ffeae934e78 EFLAGS: 00000246 ORIG_RAX: 0000000000000139 [ 13.384273] RAX: ffffffffffffffda RBX: 00005987276bfcf0 RCX: 00007a21f96ade9d [ 13.384277] RDX: 0000000000000004 RSI: 00007a21f8eda376 RDI: 000000000000001c [ 13.384280] RBP: 00007a21f8eda376 R08: 0000000000000001 R09: 00007ffeae934ec0 [ 13.384284] R10: 0000000000000050 R11: 0000000000000246 R12: 0000000000020000 [ 13.384288] R13: 00005987276c1250 R14: 0000000000000000 R15: 00005987276c4530 [ 13.384297] </TASK> [ 13.384299] Modules linked in: soundwire_amd(+) hid_sensor_gyro_3d(+) hid_sensor_magn_3d hid_sensor_accel_3d soundwire_generic_allocation amdxcp hid_sensor_trigger drm_exec industrialio_triggered_buffer soundwire_bus gpu_sched kvm_amd kfifo_buf qmi_helpers joydev drm_buddy hid_sensor_iio_common mousedev snd_soc_core industrialio i2c_algo_bit mac80211 snd_compress drm_suballoc_helper kvm snd_hda_intel drm_ttm_helper ac97_bus snd_pcm_dmaengine snd_intel_dspcfg ttm thinkpad_acpi(+) snd_intel_sdw_acpi hid_sensor_hub snd_rpl_pci_acp6x drm_display_helper snd_hda_codec hid_multitouch libarc4 snd_acp_pci platform_profile think_lmi(+) hid_generic firmware_attributes_class wmi_bmof cec snd_acp_legacy_common sparse_keymap rapl snd_hda_core psmouse cfg80211 pcspkr snd_pci_acp6x snd_hwdep video snd_pcm snd_pci_acp5x snd_timer snd_rn_pci_acp3x ucsi_acpi snd_acp_config snd sp5100_tco rfkill snd_soc_acpi typec_ucsi thunderbolt amd_sfh k10temp mhi soundcore i2c_piix4 snd_pci_acp3x typec i2c_hid_acpi roles i2c_hid wmi acpi_tad amd_pmc [ 13.384454] mac_hid i2c_dev crypto_user loop nfnetlink zram ip_tables x_tables dm_crypt cbc encrypted_keys trusted asn1_encoder tee dm_mod crct10dif_pclmul crc32_pclmul polyval_clmulni polyval_generic gf128mul ghash_clmulni_intel serio_raw sha512_ssse3 atkbd sha256_ssse3 libps2 sha1_ssse3 vivaldi_fmap nvme aesni_intel crypto_simd nvme_core cryptd ccp xhci_pci i8042 nvme_auth xhci_pci_renesas serio vfat fat btrfs blake2b_generic libcrc32c crc32c_generic crc32c_intel xor raid6_pq [ 13.384552] ---[ end trace 0000000000000000 ]--- KASAN reports a use-after-free of hid->driver_data in function amd_sfh_get_report(). The backtrace indicates that the function is called by amdtp_hid_request() which is one of the callbacks of hid device. The current make sure that driver_data is freed only once hid_destroy_device() returned. Note that I observed the crash both on v6.9.9 and v6.10.0. The code seems to be as it was from the early days of the driver. Signed-off-by: Olivier Sobrie <olivier@sobrie.be> Acked-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com> Signed-off-by: Jiri Kosina <jkosina@suse.com>
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
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In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText 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.