Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.
Will Deacon
authored
We currently route pte translation faults via do_page_fault, which elides the address check against TASK_SIZE before invoking the mm fault handling code. However, this can cause issues with the path walking code in conjunction with our word-at-a-time implementation because load_unaligned_zeropad can end up faulting in kernel space if it reads across a page boundary and runs into a page fault (e.g. by attempting to read from a guard region). In the case of such a fault, load_unaligned_zeropad has registered a fixup to shift the valid data and pad with zeroes, however the abort is reported as a level 3 translation fault and we dispatch it straight to do_page_fault, despite it being a kernel address. This results in calling a sleeping function from atomic context: BUG: sleeping function called from invalid context at arch/arm64/mm/fault.c:313 in_atomic(): 0, irqs_disabled(): 0, pid: 10290 Internal error: Oops - BUG: 0 [#1] PREEMPT SMP [...] [<ffffff8e016cd0cc>] ___might_sleep+0x134/0x144 [<ffffff8e016cd158>] __might_sleep+0x7c/0x8c [<ffffff8e016977f0>] do_page_fault+0x140/0x330 [<ffffff8e01681328>] do_mem_abort+0x54/0xb0 Exception stack(0xfffffffb20247a70 to 0xfffffffb20247ba0) [...] [<ffffff8e016844fc>] el1_da+0x18/0x78 [<ffffff8e017f399c>] path_parentat+0x44/0x88 [<ffffff8e017f4c9c>] filename_parentat+0x5c/0xd8 [<ffffff8e017f5044>] filename_create+0x4c/0x128 [<ffffff8e017f59e4>] SyS_mkdirat+0x50/0xc8 [<ffffff8e01684e30>] el0_svc_naked+0x24/0x28 Code: 36380080 d5384100 f9400800 9402566d (d4210000) ---[ end trace 2d01889f2bca9b9f ]--- Fix this by dispatching all translation faults to do_translation_faults, which avoids invoking the page fault logic for faults on kernel addresses. Cc: <stable@vger.kernel.org> Reported-by:Ankit Jain <ankijain@codeaurora.org> Signed-off-by:
Will Deacon <will.deacon@arm.com> Signed-off-by:
Catalin Marinas <catalin.marinas@arm.com>