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The tlv passed to iwl_dbg_tlv_alloc_trigger comes from a loaded firmware file. The memory can be marked as read-only as firmware could be shared. In anyway, writing to this memory is not expected. So, iwl_dbg_tlv_alloc_trigger can crash now: BUG: unable to handle page fault for address: ffffae2c01bfa794 PF: supervisor write access in kernel mode PF: error_code(0x0003) - permissions violation PGD 107d51067 P4D 107d51067 PUD 107d52067 PMD 659ad2067 PTE 8000000662298161 CPU: 2 PID: 161 Comm: kworker/2:1 Not tainted 5.7.0-3.gad96a07-default #1 openSUSE Tumbleweed (unreleased) RIP: 0010:iwl_dbg_tlv_alloc_trigger+0x25/0x60 [iwlwifi] Code: eb f2 0f 1f 00 66 66 66 66 90 83 7e 04 33 48 89 f8 44 8b 46 10 48 89 f7 76 40 41 8d 50 ff 83 fa 19 77 23 8b 56 20 85 d2 75 07 <c7> 46 20 ff ff ff ff 4b 8d 14 40 48 c1 e2 04 48 8d b4 10 00 05 00 RSP: 0018:ffffae2c00417ce8 EFLAGS: 00010246 RAX: ffff8f0522334018 RBX: ffff8f0522334018 RCX: ffffffffc0fc26c0 RDX: 0000000000000000 RSI: ffffae2c01bfa774 RDI: ffffae2c01bfa774 RBP: 0000000000000000 R08: 0000000000000004 R09: 0000000000000001 R10: 0000000000000034 R11: ffffae2c01bfa77c R12: ffff8f0522334230 R13: 0000000001000009 R14: ffff8f0523fdbc00 R15: ffff8f051f395800 FS: 0000000000000000(0000) GS:ffff8f0527c80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffae2c01bfa794 CR3: 0000000389eba000 CR4: 00000000000006e0 Call Trace: iwl_dbg_tlv_alloc+0x79/0x120 [iwlwifi] iwl_parse_tlv_firmware.isra.0+0x57d/0x1550 [iwlwifi] iwl_req_fw_callback+0x3f8/0x6a0 [iwlwifi] request_firmware_work_func+0x47/0x90 process_one_work+0x1e3/0x3b0 worker_thread+0x46/0x340 kthread+0x115/0x140 ret_from_fork+0x1f/0x40 As can be seen, write bit is not set in the PTE. Read of trig->occurrences succeeds in iwl_dbg_tlv_alloc_trigger, but trig->occurrences = cpu_to_le32(-1); fails there, obviously. This is likely because we (at SUSE) use compressed firmware and that is marked as RO after decompression (see fw_map_paged_buf). Fix it by creating a temporary buffer in case we need to change the memory. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Reported-by: Dieter Nützel <Dieter@nuetzel-hh.de> Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de> Cc: Johannes Berg <johannes.berg@intel.com> Cc: Emmanuel Grumbach <emmanuel.grumbach@intel.com> Cc: Luca Coelho <luciano.coelho@intel.com> Cc: Intel Linux Wireless <linuxwifi@intel.com> Cc: Kalle Valo <kvalo@codeaurora.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Jakub Kicinski <kuba@kernel.org> Cc: linux-wireless@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: Kalle Valo <kvalo@codeaurora.org> Link: https://lore.kernel.org/r/20200612073800.27742-1-jslaby@suse.cz
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
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text 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.