When walking through an inode extents, the ext4_ext_binsearch_idx() function
assumes that the extent header has been previously validated. However, there
are no checks that verify that the number of entries (eh->eh_entries) is
non-zero when depth is > 0. And this will lead to problems because the
EXT_FIRST_INDEX() and EXT_LAST_INDEX() will return garbage and result in this:
[ 135.245946] ------------[ cut here ]------------
[ 135.247579] kernel BUG at fs/ext4/extents.c:2258!
[ 135.249045] invalid opcode: 0000 [#1] PREEMPT SMP
[ 135.250320] CPU: 2 PID: 238 Comm: tmp118 Not tainted 5.19.0-rc8+ #4
[ 135.252067] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b-rebuilt.opensuse.org 04/01/2014
[ 135.255065] RIP: 0010:ext4_ext_map_blocks+0xc20/0xcb0
[ 135.256475] Code:
[ 135.261433] RSP: 0018:ffffc900005939f8 EFLAGS: 00010246
[ 135.262847] RAX: 0000000000000024 RBX: ffffc90000593b70 RCX: 0000000000000023
[ 135.264765] RDX: ffff8880038e5f10 RSI: 0000000000000003 RDI: ffff8880046e922c
[ 135.266670] RBP: ffff8880046e9348 R08: 0000000000000001 R09: ffff888002ca580c
[ 135.268576] R10: 0000000000002602 R11: 0000000000000000 R12: 0000000000000024
[ 135.270477] R13: 0000000000000000 R14: 0000000000000024 R15: 0000000000000000
[ 135.272394] FS: 00007fdabdc56740(0000) GS:ffff88807dd00000(0000) knlGS:0000000000000000
[ 135.274510] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 135.276075] CR2: 00007ffc26bd4f00 CR3: 0000000006261004 CR4: 0000000000170ea0
[ 135.277952] Call Trace:
[ 135.278635] <TASK>
[ 135.279247] ? preempt_count_add+0x6d/0xa0
[ 135.280358] ? percpu_counter_add_batch+0x55/0xb0
[ 135.281612] ? _raw_read_unlock+0x18/0x30
[ 135.282704] ext4_map_blocks+0x294/0x5a0
[ 135.283745] ? xa_load+0x6f/0xa0
[ 135.284562] ext4_mpage_readpages+0x3d6/0x770
[ 135.285646] read_pages+0x67/0x1d0
[ 135.286492] ? folio_add_lru+0x51/0x80
[ 135.287441] page_cache_ra_unbounded+0x124/0x170
[ 135.288510] filemap_get_pages+0x23d/0x5a0
[ 135.289457] ? path_openat+0xa72/0xdd0
[ 135.290332] filemap_read+0xbf/0x300
[ 135.291158] ? _raw_spin_lock_irqsave+0x17/0x40
[ 135.292192] new_sync_read+0x103/0x170
[ 135.293014] vfs_read+0x15d/0x180
[ 135.293745] ksys_read+0xa1/0xe0
[ 135.294461] do_syscall_64+0x3c/0x80
[ 135.295284] entry_SYSCALL_64_after_hwframe+0x46/0xb0
This patch simply adds an extra check in __ext4_ext_check(), verifying that
eh_entries is not 0 when eh_depth is > 0.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215941
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216283
Cc: Baokun Li <[email protected]>
Signed-off-by: Luís Henriques <[email protected]>
---
fs/ext4/extents.c | 4 ++++
1 file changed, 4 insertions(+)
Changes since v2:
- Dropped usage of le16_to_cpu() because we're comparing values against 0
- Use 'depth' instead of 'eh->eh_depth' because we've checked earlier that
both have the same value.
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c148bb97b527..2654fe46a1ea 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -460,6 +460,10 @@ static int __ext4_ext_check(const char *function, unsigned int line,
error_msg = "invalid eh_entries";
goto corrupted;
}
+ if (unlikely((eh->eh_entries == 0) && (eh_depth > 0))) {
+ error_msg = "eh_entries is 0 but eh_depth is > 0";
+ goto corrupted;
+ }
if (!ext4_valid_extent_entries(inode, eh, lblk, &pblk, depth)) {
error_msg = "invalid extent entries";
goto corrupted;
Hi "Lu?s,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on tytso-ext4/dev]
[also build test ERROR on linus/master v5.19 next-20220812]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Lu-s-Henriques/ext4-fix-bug-in-extents-parsing-when-eh_entries-0-and-eh_depth-0/20220812-221443
base: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
config: arm64-buildonly-randconfig-r002-20220812 (https://download.01.org/0day-ci/archive/20220813/[email protected]/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 5f1c7e2cc5a3c07cbc2412e851a7283c1841f520)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install arm64 cross compiling tool for clang build
# apt-get install binutils-aarch64-linux-gnu
# https://github.com/intel-lab-lkp/linux/commit/ef3617646de6e939d29961099c7c8adcaa0d9fd9
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Lu-s-Henriques/ext4-fix-bug-in-extents-parsing-when-eh_entries-0-and-eh_depth-0/20220812-221443
git checkout ef3617646de6e939d29961099c7c8adcaa0d9fd9
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash fs/ext4/
If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <[email protected]>
All errors (new ones prefixed by >>):
>> fs/ext4/extents.c:463:41: error: use of undeclared identifier 'eh_depth'; did you mean 'ext_depth'?
if (unlikely((eh->eh_entries == 0) && (eh_depth > 0))) {
^~~~~~~~
ext_depth
include/linux/compiler.h:78:42: note: expanded from macro 'unlikely'
# define unlikely(x) __builtin_expect(!!(x), 0)
^
fs/ext4/ext4_extents.h:192:30: note: 'ext_depth' declared here
static inline unsigned short ext_depth(struct inode *inode)
^
1 error generated.
vim +463 fs/ext4/extents.c
434
435 static int __ext4_ext_check(const char *function, unsigned int line,
436 struct inode *inode, struct ext4_extent_header *eh,
437 int depth, ext4_fsblk_t pblk, ext4_lblk_t lblk)
438 {
439 const char *error_msg;
440 int max = 0, err = -EFSCORRUPTED;
441
442 if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
443 error_msg = "invalid magic";
444 goto corrupted;
445 }
446 if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
447 error_msg = "unexpected eh_depth";
448 goto corrupted;
449 }
450 if (unlikely(eh->eh_max == 0)) {
451 error_msg = "invalid eh_max";
452 goto corrupted;
453 }
454 max = ext4_ext_max_entries(inode, depth);
455 if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
456 error_msg = "too large eh_max";
457 goto corrupted;
458 }
459 if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
460 error_msg = "invalid eh_entries";
461 goto corrupted;
462 }
> 463 if (unlikely((eh->eh_entries == 0) && (eh_depth > 0))) {
464 error_msg = "eh_entries is 0 but eh_depth is > 0";
465 goto corrupted;
466 }
467 if (!ext4_valid_extent_entries(inode, eh, lblk, &pblk, depth)) {
468 error_msg = "invalid extent entries";
469 goto corrupted;
470 }
471 if (unlikely(depth > 32)) {
472 error_msg = "too large eh_depth";
473 goto corrupted;
474 }
475 /* Verify checksum on non-root extent tree nodes */
476 if (ext_depth(inode) != depth &&
477 !ext4_extent_block_csum_verify(inode, eh)) {
478 error_msg = "extent tree corrupted";
479 err = -EFSBADCRC;
480 goto corrupted;
481 }
482 return 0;
483
484 corrupted:
485 ext4_error_inode_err(inode, function, line, 0, -err,
486 "pblk %llu bad header/extent: %s - magic %x, "
487 "entries %u, max %u(%u), depth %u(%u)",
488 (unsigned long long) pblk, error_msg,
489 le16_to_cpu(eh->eh_magic),
490 le16_to_cpu(eh->eh_entries),
491 le16_to_cpu(eh->eh_max),
492 max, le16_to_cpu(eh->eh_depth), depth);
493 return err;
494 }
495
--
0-DAY CI Kernel Test Service
https://01.org/lkp