From 1a7c3d9bb7a926e88d5f57643e75ad1abfc55013 Mon Sep 17 00:00:00 2001 From: Todd Kjos Date: Fri, 8 Feb 2019 10:35:14 -0800 Subject: [PATCH] binder: create userspace-to-binder-buffer copy function The binder driver uses a vm_area to map the per-process binder buffer space. For 32-bit android devices, this is now taking too much vmalloc space. This patch removes the use of vm_area when copying the transaction data from the sender to the buffer space. Instead of using copy_from_user() for multi-page copies, it now uses binder_alloc_copy_user_to_buffer() which uses kmap() and kunmap() to map each page, and uses copy_from_user() for copying to that page. Signed-off-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 29 +++++++-- drivers/android/binder_alloc.c | 113 +++++++++++++++++++++++++++++++++ drivers/android/binder_alloc.h | 8 +++ 3 files changed, 143 insertions(+), 7 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 01f80cbd2741..5ddb2a4d893e 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -3078,8 +3078,12 @@ static void binder_transaction(struct binder_proc *proc, ALIGN(tr->data_size, sizeof(void *))); offp = off_start; - if (copy_from_user(t->buffer->data, (const void __user *)(uintptr_t) - tr->data.ptr.buffer, tr->data_size)) { + if (binder_alloc_copy_user_to_buffer( + &target_proc->alloc, + t->buffer, 0, + (const void __user *) + (uintptr_t)tr->data.ptr.buffer, + tr->data_size)) { binder_user_error("%d:%d got transaction with invalid data ptr\n", proc->pid, thread->pid); return_error = BR_FAILED_REPLY; @@ -3087,8 +3091,13 @@ static void binder_transaction(struct binder_proc *proc, return_error_line = __LINE__; goto err_copy_data_failed; } - if (copy_from_user(offp, (const void __user *)(uintptr_t) - tr->data.ptr.offsets, tr->offsets_size)) { + if (binder_alloc_copy_user_to_buffer( + &target_proc->alloc, + t->buffer, + ALIGN(tr->data_size, sizeof(void *)), + (const void __user *) + (uintptr_t)tr->data.ptr.offsets, + tr->offsets_size)) { binder_user_error("%d:%d got transaction with invalid offsets ptr\n", proc->pid, thread->pid); return_error = BR_FAILED_REPLY; @@ -3217,6 +3226,8 @@ static void binder_transaction(struct binder_proc *proc, struct binder_buffer_object *bp = to_binder_buffer_object(hdr); size_t buf_left = sg_buf_end - sg_bufp; + binder_size_t sg_buf_offset = (uintptr_t)sg_bufp - + (uintptr_t)t->buffer->data; if (bp->length > buf_left) { binder_user_error("%d:%d got transaction with too large buffer\n", @@ -3226,9 +3237,13 @@ static void binder_transaction(struct binder_proc *proc, return_error_line = __LINE__; goto err_bad_offset; } - if (copy_from_user(sg_bufp, - (const void __user *)(uintptr_t) - bp->buffer, bp->length)) { + if (binder_alloc_copy_user_to_buffer( + &target_proc->alloc, + t->buffer, + sg_buf_offset, + (const void __user *) + (uintptr_t)bp->buffer, + bp->length)) { binder_user_error("%d:%d got transaction with invalid offsets ptr\n", proc->pid, thread->pid); return_error_param = -EFAULT; diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 022cd80e80cc..94c0d85c4e75 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -29,6 +29,8 @@ #include #include #include +#include +#include #include "binder_alloc.h" #include "binder_trace.h" @@ -1053,3 +1055,114 @@ int binder_alloc_shrinker_init(void) } return ret; } + +/** + * check_buffer() - verify that buffer/offset is safe to access + * @alloc: binder_alloc for this proc + * @buffer: binder buffer to be accessed + * @offset: offset into @buffer data + * @bytes: bytes to access from offset + * + * Check that the @offset/@bytes are within the size of the given + * @buffer and that the buffer is currently active and not freeable. + * Offsets must also be multiples of sizeof(u32). The kernel is + * allowed to touch the buffer in two cases: + * + * 1) when the buffer is being created: + * (buffer->free == 0 && buffer->allow_user_free == 0) + * 2) when the buffer is being torn down: + * (buffer->free == 0 && buffer->transaction == NULL). + * + * Return: true if the buffer is safe to access + */ +static inline bool check_buffer(struct binder_alloc *alloc, + struct binder_buffer *buffer, + binder_size_t offset, size_t bytes) +{ + size_t buffer_size = binder_alloc_buffer_size(alloc, buffer); + + return buffer_size >= bytes && + offset <= buffer_size - bytes && + IS_ALIGNED(offset, sizeof(u32)) && + !buffer->free && + (!buffer->allow_user_free || !buffer->transaction); +} + +/** + * binder_alloc_get_page() - get kernel pointer for given buffer offset + * @alloc: binder_alloc for this proc + * @buffer: binder buffer to be accessed + * @buffer_offset: offset into @buffer data + * @pgoffp: address to copy final page offset to + * + * Lookup the struct page corresponding to the address + * at @buffer_offset into @buffer->data. If @pgoffp is not + * NULL, the byte-offset into the page is written there. + * + * The caller is responsible to ensure that the offset points + * to a valid address within the @buffer and that @buffer is + * not freeable by the user. Since it can't be freed, we are + * guaranteed that the corresponding elements of @alloc->pages[] + * cannot change. + * + * Return: struct page + */ +static struct page *binder_alloc_get_page(struct binder_alloc *alloc, + struct binder_buffer *buffer, + binder_size_t buffer_offset, + pgoff_t *pgoffp) +{ + binder_size_t buffer_space_offset = buffer_offset + + (buffer->data - alloc->buffer); + pgoff_t pgoff = buffer_space_offset & ~PAGE_MASK; + size_t index = buffer_space_offset >> PAGE_SHIFT; + struct binder_lru_page *lru_page; + + lru_page = &alloc->pages[index]; + *pgoffp = pgoff; + return lru_page->page_ptr; +} + +/** + * binder_alloc_copy_user_to_buffer() - copy src user to tgt user + * @alloc: binder_alloc for this proc + * @buffer: binder buffer to be accessed + * @buffer_offset: offset into @buffer data + * @from: userspace pointer to source buffer + * @bytes: bytes to copy + * + * Copy bytes from source userspace to target buffer. + * + * Return: bytes remaining to be copied + */ +unsigned long +binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc, + struct binder_buffer *buffer, + binder_size_t buffer_offset, + const void __user *from, + size_t bytes) +{ + if (!check_buffer(alloc, buffer, buffer_offset, bytes)) + return bytes; + + while (bytes) { + unsigned long size; + unsigned long ret; + struct page *page; + pgoff_t pgoff; + void *kptr; + + page = binder_alloc_get_page(alloc, buffer, + buffer_offset, &pgoff); + size = min_t(size_t, bytes, PAGE_SIZE - pgoff); + kptr = kmap(page) + pgoff; + ret = copy_from_user(kptr, from, size); + kunmap(page); + if (ret) + return bytes - size + ret; + bytes -= size; + from += size; + buffer_offset += size; + } + return 0; +} diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h index c0aadbbf7f19..995155f31dbd 100644 --- a/drivers/android/binder_alloc.h +++ b/drivers/android/binder_alloc.h @@ -22,6 +22,7 @@ #include #include #include +#include extern struct list_lru binder_alloc_lru; struct binder_transaction; @@ -183,5 +184,12 @@ binder_alloc_get_user_buffer_offset(struct binder_alloc *alloc) return alloc->user_buffer_offset; } +unsigned long +binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc, + struct binder_buffer *buffer, + binder_size_t buffer_offset, + const void __user *from, + size_t bytes); + #endif /* _LINUX_BINDER_ALLOC_H */