[Syz log]
SQUASHFS error: Failed to read block 0x6fc: -5
SQUASHFS error: Unable to read metadata cache entry [6fa]
SQUASHFS error: Unable to read metadata cache entry [6fa]
SQUASHFS error: Unable to read metadata cache entry [6fa]
==================================================================
BUG: KASAN: slab-out-of-bounds in __readahead_batch include/linux/pagemap.h:1364 [inline]
BUG: KASAN: slab-out-of-bounds in squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
Write of size 8 at addr ffff88801e393648 by task syz-executor100/5067
CPU: 1 PID: 5067 Comm: syz-executor100 Not tainted 6.6.0-syzkaller-15156-g13d88ac54ddd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0x163/0x540 mm/kasan/report.c:475
kasan_report+0x142/0x170 mm/kasan/report.c:588
__readahead_batch include/linux/pagemap.h:1364 [inline]
squashfs_readahead+0x9a6/0x20d0 fs/squashfs/file.c:569
read_pages+0x183/0x830 mm/readahead.c:160
page_cache_ra_unbounded+0x68e/0x7c0 mm/readahead.c:269
page_cache_sync_readahead include/linux/pagemap.h:1266 [inline]
filemap_get_pages+0x49c/0x2080 mm/filemap.c:2497
filemap_read+0x42b/0x10b0 mm/filemap.c:2593
__kernel_read+0x425/0x8b0 fs/read_write.c:428
integrity_kernel_read+0xb0/0xf0 security/integrity/iint.c:221
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
ima_calc_file_hash+0xad1/0x1b30 security/integrity/ima/ima_crypto.c:573
ima_collect_measurement+0x554/0xb30 security/integrity/ima/ima_api.c:290
process_measurement+0x1373/0x21c0 security/integrity/ima/ima_main.c:359
ima_file_check+0xf1/0x170 security/integrity/ima/ima_main.c:557
do_open fs/namei.c:3624 [inline]
path_openat+0x2893/0x3280 fs/namei.c:3779
[Bug]
path_openat() called open_last_lookups() before calling do_open() and
open_last_lookups() will eventually call squashfs_read_inode() to set
inode->i_size, but before setting i_size, it is necessary to obtain file_size
from the disk.
However, during the value retrieval process, the length of the value retrieved
from the disk was greater than output->length, resulting(-EIO) in the failure of
squashfs_read_data(), further leading to i_size has not been initialized,
i.e. its value is 0.
This resulted in the failure of squashfs_read_data(), where "SQUASHFS error:
Failed to read block 0x6fc: -5" was output in the syz log.
This also resulted in the failure of squashfs_cache_get(), outputting "SQUASHFS
error: Unable to read metadata cache entry [6fa]" in the syz log.
[Fix]
Before performing a read ahead operation in squashfs_read_folio() and
squashfs_readahead(), check if i_size is not 0 before continuing.
Optimize the return value of squashfs_read_data() and return -EFBIG when the
length is greater than output->length(or (index + length) >
msblk->bytes_used).
Reported-and-tested-by: syzbot+604424eb051c2f696163@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: f268eedddf35 ("squashfs: extend "page actor" to handle missing pages")
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
fs/squashfs/block.c | 2 +-
fs/squashfs/file.c | 8 ++++++++
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index 581ce9519339..d335f28c822c 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -323,7 +323,7 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
}
if (length < 0 || length > output->length ||
(index + length) > msblk->bytes_used) {
- res = -EIO;
+ res = length < 0 ? -EIO : -EFBIG;
goto out;
}
diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index 8ba8c4c50770..5472ddd3596c 100644
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -461,6 +461,11 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
page->index, squashfs_i(inode)->start);
+ if (!file_end) {
+ res = -EINVAL;
+ goto out;
+ }
+
if (page->index >= ((i_size_read(inode) + PAGE_SIZE - 1) >>
PAGE_SHIFT))
goto out;
@@ -547,6 +552,9 @@ static void squashfs_readahead(struct readahead_control *ractl)
int i, file_end = i_size_read(inode) >> msblk->block_log;
unsigned int max_pages = 1UL << shift;
+ if (!file_end)
+ return;
+
readahead_expand(ractl, start, (len | mask) + 1);
pages = kmalloc_array(max_pages, sizeof(void *), GFP_KERNEL);
--
2.25.1
