The patch titled Subject: exec: open code copy_string_kernel has been added to the -mm tree. Its filename is exec-open-code-copy_string_kernel.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/exec-open-code-copy_string_kernel.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/exec-open-code-copy_string_kernel.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Christoph Hellwig <hch@xxxxxx> Subject: exec: open code copy_string_kernel Currently copy_string_kernel is just a wrapper around copy_strings that simplifies the calling conventions and uses set_fs to allow passing a kernel pointer. But due to the fact the we only need to handle a single kernel argument pointer, the logic can be sigificantly simplified while getting rid of the set_fs. Link: http://lkml.kernel.org/r/20200501104105.2621149-3-hch@xxxxxx Signed-off-by: Christoph Hellwig <hch@xxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/exec.c | 45 +++++++++++++++++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 10 deletions(-) --- a/fs/exec.c~exec-open-code-copy_string_kernel +++ a/fs/exec.c @@ -592,17 +592,42 @@ out: */ int copy_string_kernel(const char *arg, struct linux_binprm *bprm) { - int r; - mm_segment_t oldfs = get_fs(); - struct user_arg_ptr argv = { - .ptr.native = (const char __user *const __user *)&arg, - }; - - set_fs(KERNEL_DS); - r = copy_strings(1, argv, bprm); - set_fs(oldfs); + int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */; + unsigned long pos = bprm->p; - return r; + if (len == 0) + return -EFAULT; + if (!valid_arg_len(bprm, len)) + return -E2BIG; + + /* We're going to work our way backwards. */ + arg += len; + bprm->p -= len; + if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin) + return -E2BIG; + + while (len > 0) { + unsigned int bytes_to_copy = min_t(unsigned int, len, + min_not_zero(offset_in_page(pos), PAGE_SIZE)); + struct page *page; + char *kaddr; + + pos -= bytes_to_copy; + arg -= bytes_to_copy; + len -= bytes_to_copy; + + page = get_arg_page(bprm, pos, 1); + if (!page) + return -E2BIG; + kaddr = kmap_atomic(page); + flush_arg_page(bprm, pos & PAGE_MASK, page); + memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy); + flush_kernel_dcache_page(page); + kunmap_atomic(kaddr); + put_arg_page(page); + } + + return 0; } EXPORT_SYMBOL(copy_string_kernel); _ Patches currently in -mm which might be from hch@xxxxxx are x86-hyperv-use-vmalloc_exec-for-the-hypercall-page.patch x86-fix-vmap-arguments-in-map_irq_stack.patch staging-android-ion-use-vmap-instead-of-vm_map_ram.patch staging-media-ipu3-use-vmap-instead-of-reimplementing-it.patch dma-mapping-use-vmap-insted-of-reimplementing-it.patch powerpc-add-an-ioremap_phb-helper.patch powerpc-remove-__ioremap_at-and-__iounmap_at.patch mm-remove-__get_vm_area.patch mm-unexport-unmap_kernel_range_noflush.patch mm-rename-config_pgtable_mapping-to-config_zsmalloc_pgtable_mapping.patch mm-only-allow-page-table-mappings-for-built-in-zsmalloc.patch mm-pass-addr-as-unsigned-long-to-vb_free.patch mm-remove-vmap_page_range_noflush-and-vunmap_page_range.patch mm-rename-vmap_page_range-to-map_kernel_range.patch mm-dont-return-the-number-of-pages-from-map_kernel_range_noflush.patch mm-remove-map_vm_range.patch mm-remove-unmap_vmap_area.patch mm-remove-the-prot-argument-from-vm_map_ram.patch mm-enforce-that-vmap-cant-map-pages-executable.patch gpu-drm-remove-the-powerpc-hack-in-drm_legacy_sg_alloc.patch mm-remove-the-pgprot-argument-to-__vmalloc.patch mm-remove-the-prot-argument-to-__vmalloc_node.patch mm-remove-both-instances-of-__vmalloc_node_flags.patch mm-remove-__vmalloc_node_flags_caller.patch mm-switch-the-test_vmalloc-module-to-use-__vmalloc_node.patch mm-remove-vmalloc_user_node_flags.patch arm64-use-__vmalloc_node-in-arch_alloc_vmap_stack.patch powerpc-use-__vmalloc_node-in-alloc_vm_stack.patch s390-use-__vmalloc_node-in-stack_alloc.patch exec-simplify-the-copy_strings_kernel-calling-convention.patch exec-open-code-copy_string_kernel.patch amdgpu-a-null-mm-does-not-mean-a-thread-is-a-kthread.patch kernel-move-use_mm-unuse_mm-to-kthreadc.patch kernel-move-use_mm-unuse_mm-to-kthreadc-v2.patch kernel-better-document-the-use_mm-unuse_mm-api-contract.patch kernel-better-document-the-use_mm-unuse_mm-api-contract-v2.patch kernel-set-user_ds-in-kthread_use_mm.patch