From 5dc54a06f6e575f146492661129d24f3b50d17bb Mon Sep 17 00:00:00 2001 From: "Joel Fernandes (Google)" Date: Mon, 30 Sep 2019 16:12:50 -0400 Subject: binder: Fix comment headers on binder_alloc_prepare_to_free() binder_alloc_buffer_lookup() doesn't exist and is named "binder_alloc_prepare_to_free()". Correct the code comments to reflect this. Signed-off-by: Joel Fernandes (Google) Reviewed-by: Christian Brauner Link: https://lore.kernel.org/r/20190930201250.139554-1-joel@joelfernandes.org Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/android/binder_alloc.c') diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 6d79a1b0d446..d42a8b2f636a 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -156,7 +156,7 @@ static struct binder_buffer *binder_alloc_prepare_to_free_locked( } /** - * binder_alloc_buffer_lookup() - get buffer given user ptr + * binder_alloc_prepare_to_free() - get buffer given user ptr * @alloc: binder_alloc for this proc * @user_ptr: User pointer to buffer data * -- cgit v1.3-14-g43fede From 45d02f79b539073b76077836871de6b674e36eb4 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Wed, 16 Oct 2019 17:01:18 +0200 Subject: binder: Don't modify VMA bounds in ->mmap handler binder_mmap() tries to prevent the creation of overly big binder mappings by silently truncating the size of the VMA to 4MiB. However, this violates the API contract of mmap(). If userspace attempts to create a large binder VMA, and later attempts to unmap that VMA, it will call munmap() on a range beyond the end of the VMA, which may have been allocated to another VMA in the meantime. This can lead to userspace memory corruption. The following sequence of calls leads to a segfault without this commit: int main(void) { int binder_fd = open("/dev/binder", O_RDWR); if (binder_fd == -1) err(1, "open binder"); void *binder_mapping = mmap(NULL, 0x800000UL, PROT_READ, MAP_SHARED, binder_fd, 0); if (binder_mapping == MAP_FAILED) err(1, "mmap binder"); void *data_mapping = mmap(NULL, 0x400000UL, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); if (data_mapping == MAP_FAILED) err(1, "mmap data"); munmap(binder_mapping, 0x800000UL); *(char*)data_mapping = 1; return 0; } Cc: stable@vger.kernel.org Signed-off-by: Jann Horn Acked-by: Todd Kjos Acked-by: Christian Brauner Link: https://lore.kernel.org/r/20191016150119.154756-1-jannh@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 7 ------- drivers/android/binder_alloc.c | 6 ++++-- 2 files changed, 4 insertions(+), 9 deletions(-) (limited to 'drivers/android/binder_alloc.c') diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 5b9ac2122e89..265d9dd46a5e 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -97,10 +97,6 @@ DEFINE_SHOW_ATTRIBUTE(proc); #define SZ_1K 0x400 #endif -#ifndef SZ_4M -#define SZ_4M 0x400000 -#endif - #define FORBIDDEN_MMAP_FLAGS (VM_WRITE) enum { @@ -5177,9 +5173,6 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma) if (proc->tsk != current->group_leader) return -EINVAL; - if ((vma->vm_end - vma->vm_start) > SZ_4M) - vma->vm_end = vma->vm_start + SZ_4M; - binder_debug(BINDER_DEBUG_OPEN_CLOSE, "%s: %d %lx-%lx (%ld K) vma %lx pagep %lx\n", __func__, proc->pid, vma->vm_start, vma->vm_end, diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index d42a8b2f636a..eb76a823fbb2 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -22,6 +22,7 @@ #include #include #include +#include #include "binder_alloc.h" #include "binder_trace.h" @@ -689,7 +690,9 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, alloc->buffer = (void __user *)vma->vm_start; mutex_unlock(&binder_alloc_mmap_lock); - alloc->pages = kcalloc((vma->vm_end - vma->vm_start) / PAGE_SIZE, + alloc->buffer_size = min_t(unsigned long, vma->vm_end - vma->vm_start, + SZ_4M); + alloc->pages = kcalloc(alloc->buffer_size / PAGE_SIZE, sizeof(alloc->pages[0]), GFP_KERNEL); if (alloc->pages == NULL) { @@ -697,7 +700,6 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, failure_string = "alloc page array"; goto err_alloc_pages_failed; } - alloc->buffer_size = vma->vm_end - vma->vm_start; buffer = kzalloc(sizeof(*buffer), GFP_KERNEL); if (!buffer) { -- cgit v1.3-14-g43fede