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| author | Carlos Llamas <cmllamas@google.com> | 2024-12-10 14:31:01 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-12-24 09:35:23 +0100 |
| commit | 072010abc3ad98bc20198dbe60ef13233a0a357c (patch) | |
| tree | 767cacda44b98f3044b3eaf850aeb18ed64a6108 /drivers/android/binder_alloc.c | |
| parent | f909f0308267dc49fbf122f60e1ec7ddcd1b92c7 (diff) | |
| download | lwn-072010abc3ad98bc20198dbe60ef13233a0a357c.tar.gz lwn-072010abc3ad98bc20198dbe60ef13233a0a357c.zip | |
binder: replace alloc->vma with alloc->mapped
It is unsafe to use alloc->vma outside of the mmap_sem. Instead, add a
new boolean alloc->mapped to save the vma state (mapped or unmmaped) and
use this as a replacement for alloc->vma to validate several paths.
Using the alloc->vma caused several performance and security issues in
the past. Now that it has been replaced with either vm_lookup() or the
alloc->mapped state, we can finally remove it.
Cc: Minchan Kim <minchan@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20241210143114.661252-6-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android/binder_alloc.c')
| -rw-r--r-- | drivers/android/binder_alloc.c | 48 |
1 files changed, 26 insertions, 22 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 3e30ac5b4861..ed79d7c146c8 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -220,6 +220,19 @@ static void binder_lru_freelist_add(struct binder_alloc *alloc, } } +static inline +void binder_alloc_set_mapped(struct binder_alloc *alloc, bool state) +{ + /* pairs with smp_load_acquire in binder_alloc_is_mapped() */ + smp_store_release(&alloc->mapped, state); +} + +static inline bool binder_alloc_is_mapped(struct binder_alloc *alloc) +{ + /* pairs with smp_store_release in binder_alloc_set_mapped() */ + return smp_load_acquire(&alloc->mapped); +} + static struct page *binder_page_alloc(struct binder_alloc *alloc, unsigned long index) { @@ -271,7 +284,7 @@ static int binder_install_single_page(struct binder_alloc *alloc, mmap_read_lock(alloc->mm); vma = vma_lookup(alloc->mm, addr); - if (!vma || vma != alloc->vma) { + if (!vma || !binder_alloc_is_mapped(alloc)) { binder_free_page(page); pr_err("%d: %s failed, no vma\n", alloc->pid, __func__); ret = -ESRCH; @@ -379,20 +392,6 @@ static void binder_lru_freelist_del(struct binder_alloc *alloc, } } -static inline void binder_alloc_set_vma(struct binder_alloc *alloc, - struct vm_area_struct *vma) -{ - /* pairs with smp_load_acquire in binder_alloc_get_vma() */ - smp_store_release(&alloc->vma, vma); -} - -static inline struct vm_area_struct *binder_alloc_get_vma( - struct binder_alloc *alloc) -{ - /* pairs with smp_store_release in binder_alloc_set_vma() */ - return smp_load_acquire(&alloc->vma); -} - static void debug_no_space_locked(struct binder_alloc *alloc) { size_t largest_alloc_size = 0; @@ -626,7 +625,7 @@ struct binder_buffer *binder_alloc_new_buf(struct binder_alloc *alloc, int ret; /* Check binder_alloc is fully initialized */ - if (!binder_alloc_get_vma(alloc)) { + if (!binder_alloc_is_mapped(alloc)) { binder_alloc_debug(BINDER_DEBUG_USER_ERROR, "%d: binder_alloc_buf, no vma\n", alloc->pid); @@ -908,7 +907,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, alloc->free_async_space = alloc->buffer_size / 2; /* Signal binder_alloc is fully initialized */ - binder_alloc_set_vma(alloc, vma); + binder_alloc_set_mapped(alloc, true); return 0; @@ -938,7 +937,7 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc) buffers = 0; mutex_lock(&alloc->mutex); - BUG_ON(alloc->vma); + BUG_ON(alloc->mapped); while ((n = rb_first(&alloc->allocated_buffers))) { buffer = rb_entry(n, struct binder_buffer, rb_node); @@ -1044,7 +1043,7 @@ void binder_alloc_print_pages(struct seq_file *m, * Make sure the binder_alloc is fully initialized, otherwise we might * read inconsistent state. */ - if (binder_alloc_get_vma(alloc) != NULL) { + if (binder_alloc_is_mapped(alloc)) { for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) { page = binder_get_installed_page(alloc, i); if (!page) @@ -1084,12 +1083,12 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc) * @alloc: binder_alloc for this proc * * Called from binder_vma_close() when releasing address space. - * Clears alloc->vma to prevent new incoming transactions from + * Clears alloc->mapped to prevent new incoming transactions from * allocating more buffers. */ void binder_alloc_vma_close(struct binder_alloc *alloc) { - binder_alloc_set_vma(alloc, NULL); + binder_alloc_set_mapped(alloc, false); } /** @@ -1125,7 +1124,12 @@ enum lru_status binder_alloc_free_page(struct list_head *item, page_addr = alloc->buffer + index * PAGE_SIZE; vma = vma_lookup(mm, page_addr); - if (vma && vma != binder_alloc_get_vma(alloc)) + /* + * Since a binder_alloc can only be mapped once, we ensure + * the vma corresponds to this mapping by checking whether + * the binder_alloc is still mapped. + */ + if (vma && !binder_alloc_is_mapped(alloc)) goto err_invalid_vma; trace_binder_unmap_kernel_start(alloc, index); |