The patch titled
Subject: mm: fs: initialize fsdata passed to write_begin/write_end interface
has been added to the -mm mm-unstable branch. Its filename is
mm-fs-initialize-fsdata-passed-to-write_begin-write_end-interface.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fs-initialize-fsdata-passed-to-write_begin-write_end-interface.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: mm: fs: initialize fsdata passed to write_begin/write_end interface
Date: Fri, 26 Aug 2022 17:08:06 +0200
Functions implementing the a_ops->write_end() interface accept the `void
*fsdata` parameter that is supposed to be initialized by the corresponding
a_ops->write_begin() (which accepts `void **fsdata`).
However not all a_ops->write_begin() implementations initialize `fsdata`
unconditionally, so it may get passed uninitialized to a_ops->write_end(),
resulting in undefined behavior.
Fix this by initializing fsdata with NULL before the call to
write_begin(), rather than doing so in all possible a_ops implementations.
This patch covers only the following cases found by running x86 KMSAN
under syzkaller:
- generic_perform_write()
- cont_expand_zero() and generic_cont_expand_simple()
- page_symlink()
Other cases of passing uninitialized fsdata may persist in the codebase.
Link: https://lkml.kernel.org/r/20220826150807.723137-44-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/buffer.c | 4 ++--
fs/namei.c | 2 +-
mm/filemap.c | 2 +-
3 files changed, 4 insertions(+), 4 deletions(-)
--- a/fs/buffer.c~mm-fs-initialize-fsdata-passed-to-write_begin-write_end-interface
+++ a/fs/buffer.c
@@ -2352,7 +2352,7 @@ int generic_cont_expand_simple(struct in
struct address_space *mapping = inode->i_mapping;
const struct address_space_operations *aops = mapping->a_ops;
struct page *page;
- void *fsdata;
+ void *fsdata = NULL;
int err;
err = inode_newsize_ok(inode, size);
@@ -2378,7 +2378,7 @@ static int cont_expand_zero(struct file
const struct address_space_operations *aops = mapping->a_ops;
unsigned int blocksize = i_blocksize(inode);
struct page *page;
- void *fsdata;
+ void *fsdata = NULL;
pgoff_t index, curidx;
loff_t curpos;
unsigned zerofrom, offset, len;
--- a/fs/namei.c~mm-fs-initialize-fsdata-passed-to-write_begin-write_end-interface
+++ a/fs/namei.c
@@ -5088,7 +5088,7 @@ int page_symlink(struct inode *inode, co
const struct address_space_operations *aops = mapping->a_ops;
bool nofs = !mapping_gfp_constraint(mapping, __GFP_FS);
struct page *page;
- void *fsdata;
+ void *fsdata = NULL;
int err;
unsigned int flags;
--- a/mm/filemap.c~mm-fs-initialize-fsdata-passed-to-write_begin-write_end-interface
+++ a/mm/filemap.c
@@ -3706,7 +3706,7 @@ ssize_t generic_perform_write(struct kio
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
size_t copied; /* Bytes copied from user */
- void *fsdata;
+ void *fsdata = NULL;
offset = (pos & (PAGE_SIZE - 1));
bytes = min_t(unsigned long, PAGE_SIZE - offset,
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
stackdepot-reserve-5-extra-bits-in-depot_stack_handle_t.patch
instrumentedh-allow-instrumenting-both-sides-of-copy_from_user.patch
x86-asm-instrument-usercopy-in-get_user-and-put_user.patch
asm-generic-instrument-usercopy-in-cacheflushh.patch
kmsan-add-rest-documentation.patch
kmsan-introduce-__no_sanitize_memory-and-__no_kmsan_checks.patch
kmsan-mark-noinstr-as-__no_sanitize_memory.patch
x86-kmsan-pgtable-reduce-vmalloc-space.patch
libnvdimm-pfn_dev-increase-max_struct_page_size.patch
kmsan-add-kmsan-runtime-core.patch
kmsan-disable-instrumentation-of-unsupported-common-kernel-code.patch
maintainers-add-entry-for-kmsan.patch
mm-kmsan-maintain-kmsan-metadata-for-page-operations.patch
mm-kmsan-call-kmsan-hooks-from-slub-code.patch
kmsan-handle-task-creation-and-exiting.patch
init-kmsan-call-kmsan-initialization-routines.patch
instrumentedh-add-kmsan-support.patch
kmsan-unpoison-tlb-in-arch_tlb_gather_mmu.patch
kmsan-add-iomap-support.patch
input-libps2-mark-data-received-in-__ps2_command-as-initialized.patch
dma-kmsan-unpoison-dma-mappings.patch
virtio-kmsan-check-unpoison-scatterlist-in-vring_map_one_sg.patch
kmsan-handle-memory-sent-to-from-usb.patch
kmsan-add-tests-for-kmsan.patch
kmsan-disable-strscpy-optimization-under-kmsan.patch
crypto-kmsan-disable-accelerated-configs-under-kmsan.patch
kmsan-disable-physical-page-merging-in-biovec.patch
block-kmsan-skip-bio-block-merging-logic-for-kmsan.patch
kcov-kmsan-unpoison-area-list-in-kcov_remote_area_put.patch
security-kmsan-fix-interoperability-with-auto-initialization.patch
objtool-kmsan-list-kmsan-api-functions-as-uaccess-safe.patch
x86-kmsan-disable-instrumentation-of-unsupported-code.patch
x86-kmsan-skip-shadow-checks-in-__switch_to.patch
x86-kmsan-handle-open-coded-assembly-in-lib-iomemc.patch
x86-kmsan-use-__msan_-string-functions-where-possible.patch
x86-kmsan-sync-metadata-pages-on-page-fault.patch
x86-kasan-kmsan-support-config_generic_csum-on-x86-enable-it-for-kasan-kmsan.patch
x86-fs-kmsan-disable-config_dcache_word_access.patch
x86-kmsan-dont-instrument-stack-walking-functions.patch
entry-kmsan-introduce-kmsan_unpoison_entry_regs.patch
bpf-kmsan-initialize-bpf-registers-with-zeroes.patch
mm-fs-initialize-fsdata-passed-to-write_begin-write_end-interface.patch
x86-kmsan-enable-kmsan-builds-for-x86.patch
