As Paul Bandha reported in bugzilla:
https://bugzilla.kernel.org/show_bug.cgi?id=202709
When I run the poc on the mounted f2fs img I get a buffer overflow in
read_inline_xattr due to there being no sanity check on the value of
i_inline_xattr_size.
I created the img by just modifying the value of i_inline_xattr_size
in the inode:
i_name [test1.txt]
i_ext: fofs:0 blkaddr:0 len:0
i_extra_isize [0x 18 : 24]
i_inline_xattr_size [0x ffff : 65535]
i_addr[ofs] [0x 0 : 0]
mkdir /mnt/f2fs
mount ./f2fs1.img /mnt/f2fs
gcc poc.c -o poc
./poc
int main() {
int y = syscall(SYS_listxattr, "/mnt/f2fs/test1.txt", NULL, 0);
printf("ret %d", y);
printf("errno: %d\n", errno);
}
BUG: KASAN: slab-out-of-bounds in read_inline_xattr+0x18f/0x260
Read of size 262140 at addr
ffff88011035efd8 by task f2fs1poc/3263
CPU: 0 PID: 3263 Comm: f2fs1poc Not tainted 4.18.0-custom #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.11.1-0-g0551a4be2c-prebuilt.qemu-project.org 04/01/2014
Call Trace:
dump_stack+0x71/0xab
print_address_description+0x83/0x250
kasan_report+0x213/0x350
memcpy+0x1f/0x50
read_inline_xattr+0x18f/0x260
read_all_xattrs+0xba/0x190
f2fs_listxattr+0x9d/0x3f0
listxattr+0xb2/0xd0
path_listxattr+0x93/0xe0
do_syscall_64+0x9d/0x220
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Let's add sanity check for inode.i_inline_xattr_size during f2fs_iget()
to avoid this issue.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
#include "f2fs.h"
#include "node.h"
#include "segment.h"
+#include "xattr.h"
#include <trace/events/f2fs.h>
return false;
}
+ if (f2fs_has_extra_attr(inode) &&
+ f2fs_sb_has_flexible_inline_xattr(sbi) &&
+ f2fs_has_inline_xattr(inode) &&
+ (!fi->i_inline_xattr_size ||
+ fi->i_inline_xattr_size > MAX_INLINE_XATTR_SIZE)) {
+ set_sbi_flag(sbi, SBI_NEED_FSCK);
+ f2fs_msg(sbi->sb, KERN_WARNING,
+ "%s: inode (ino=%lx) has corrupted "
+ "i_inline_xattr_size: %d, max: %zu",
+ __func__, inode->i_ino, fi->i_inline_xattr_size,
+ MAX_INLINE_XATTR_SIZE);
+ return false;
+ }
+
if (F2FS_I(inode)->extent_tree) {
struct extent_info *ei = &F2FS_I(inode)->extent_tree->largest;
}
min_size = sizeof(struct f2fs_xattr_header) / sizeof(__le32);
- max_size = DEF_ADDRS_PER_INODE -
- F2FS_TOTAL_EXTRA_ATTR_SIZE / sizeof(__le32) -
- DEF_INLINE_RESERVED_SIZE -
- MIN_INLINE_DENTRY_SIZE / sizeof(__le32);
+ max_size = MAX_INLINE_XATTR_SIZE;
if (F2FS_OPTION(sbi).inline_xattr_size < min_size ||
F2FS_OPTION(sbi).inline_xattr_size > max_size) {
sizeof(struct f2fs_xattr_header) - \
sizeof(struct f2fs_xattr_entry))
+#define MAX_INLINE_XATTR_SIZE \
+ (DEF_ADDRS_PER_INODE - \
+ F2FS_TOTAL_EXTRA_ATTR_SIZE / sizeof(__le32) - \
+ DEF_INLINE_RESERVED_SIZE - \
+ MIN_INLINE_DENTRY_SIZE / sizeof(__le32))
+
/*
* On-disk structure of f2fs_xattr
* We use inline xattrs space + 1 block for xattr.