From 1e1ff4ce9cd70dc34d9ef15f9c054ee4d993beea Mon Sep 17 00:00:00 2001 From: Romain Perier Date: Sat, 20 Jul 2019 18:36:49 +0200 Subject: [PATCH] binder: fix race between munmap() and direct reclaim (CVE-2019-1999) --- debian/changelog | 1 + ...ce-between-munmap-and-direct-reclaim.patch | 68 +++++++++++++++++++ debian/patches/series | 1 + 3 files changed, 70 insertions(+) create mode 100644 debian/patches/bugfix/all/binder-fix-race-between-munmap-and-direct-reclaim.patch diff --git a/debian/changelog b/debian/changelog index e3e299d8a..6bb3f9e20 100644 --- a/debian/changelog +++ b/debian/changelog @@ -16,6 +16,7 @@ linux (4.19.37-6) UNRELEASED; urgency=medium * [powerpc*] mm/64s/hash: Reallocate context ids on fork (CVE-2019-12817) * nfc: Ensure presence of required attributes in the deactivate_target handler (CVE-2019-12984) + * binder: fix race between munmap() and direct reclaim (CVE-2019-1999) -- Salvatore Bonaccorso Sun, 23 Jun 2019 16:15:17 +0200 diff --git a/debian/patches/bugfix/all/binder-fix-race-between-munmap-and-direct-reclaim.patch b/debian/patches/bugfix/all/binder-fix-race-between-munmap-and-direct-reclaim.patch new file mode 100644 index 000000000..1143ac8c3 --- /dev/null +++ b/debian/patches/bugfix/all/binder-fix-race-between-munmap-and-direct-reclaim.patch @@ -0,0 +1,68 @@ +From 37b68ba30a93ee10b2e0531affdab9665dbe7b80 Mon Sep 17 00:00:00 2001 +From: Todd Kjos +Date: Fri, 1 Mar 2019 15:06:06 -0800 +Subject: [PATCH] binder: fix race between munmap() and direct reclaim +Origin: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=5cec2d2e5839f9c0fec319c523a911e0a7fd299f +Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2019-1999 + +An munmap() on a binder device causes binder_vma_close() to be called +which clears the alloc->vma pointer. + +If direct reclaim causes binder_alloc_free_page() to be called, there +is a race where alloc->vma is read into a local vma pointer and then +used later after the mm->mmap_sem is acquired. This can result in +calling zap_page_range() with an invalid vma which manifests as a +use-after-free in zap_page_range(). + +The fix is to check alloc->vma after acquiring the mmap_sem (which we +were acquiring anyway) and skip zap_page_range() if it has changed +to NULL. + +Signed-off-by: Todd Kjos +Reviewed-by: Joel Fernandes (Google) +Cc: stable +Signed-off-by: Greg Kroah-Hartman +--- + drivers/android/binder_alloc.c | 17 ++++++++--------- + 1 file changed, 8 insertions(+), 9 deletions(-) + +diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c +index 030c98f35cca..3863ef78e40f 100644 +--- a/drivers/android/binder_alloc.c ++++ b/drivers/android/binder_alloc.c +@@ -958,14 +958,13 @@ enum lru_status binder_alloc_free_page(struct list_head *item, + + index = page - alloc->pages; + page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE; ++ ++ mm = alloc->vma_vm_mm; ++ if (!mmget_not_zero(mm)) ++ goto err_mmget; ++ if (!down_write_trylock(&mm->mmap_sem)) ++ goto err_down_write_mmap_sem_failed; + vma = binder_alloc_get_vma(alloc); +- if (vma) { +- if (!mmget_not_zero(alloc->vma_vm_mm)) +- goto err_mmget; +- mm = alloc->vma_vm_mm; +- if (!down_write_trylock(&mm->mmap_sem)) +- goto err_down_write_mmap_sem_failed; +- } + + list_lru_isolate(lru, item); + spin_unlock(lock); +@@ -979,9 +978,9 @@ enum lru_status binder_alloc_free_page(struct list_head *item, + + trace_binder_unmap_user_end(alloc, index); + +- up_write(&mm->mmap_sem); +- mmput(mm); + } ++ up_write(&mm->mmap_sem); ++ mmput(mm); + + trace_binder_unmap_kernel_start(alloc, index); + +-- +2.20.1 + diff --git a/debian/patches/series b/debian/patches/series index 101206396..81454443d 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -233,6 +233,7 @@ bugfix/all/ptrace-Fix-ptracer_cred-handling-for-PTRACE_TRACEME.patch bugfix/x86/x86-insn-eval-Fix-use-after-free-access-to-LDT-entry.patch bugfix/powerpc/powerpc-mm-64s-hash-Reallocate-context-ids-on-fork.patch bugfix/all/nfc-Ensure-presence-of-required-attributes-in-the-deactivate_target.patch +bugfix/all/binder-fix-race-between-munmap-and-direct-reclaim.patch # Fix exported symbol versions bugfix/all/module-disable-matching-missing-version-crc.patch