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Date: Mon, 4 Mar 2019 14:43:08 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Sahitya Tummala <stummala@...eaurora.org>
CC: <jaegeuk@...nel.org>, <linux-kernel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix to do sanity check with
inode.i_inline_xattr_size
Hi Sahitya,
On 2019/3/4 11:59, Sahitya Tummala wrote:
> On Fri, Mar 01, 2019 at 03:38:05PM +0800, Chao Yu wrote:
>> 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@...wei.com>
>> ---
>> fs/f2fs/inode.c | 14 ++++++++++++++
>> fs/f2fs/super.c | 7 ++-----
>> fs/f2fs/xattr.h | 9 +++++++++
>> 3 files changed, 25 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>> index bec52961630b..b132fe2ff779 100644
>> --- a/fs/f2fs/inode.c
>> +++ b/fs/f2fs/inode.c
>> @@ -14,6 +14,7 @@
>> #include "f2fs.h"
>> #include "node.h"
>> #include "segment.h"
>> +#include "xattr.h"
>>
>> #include <trace/events/f2fs.h>
>>
>> @@ -248,6 +249,19 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
>> return false;
>> }
>>
>> + if (f2fs_has_extra_attr(inode) &&
>> + f2fs_sb_has_flexible_inline_xattr(sbi) &&
>> + (fi->i_inline_xattr_size < MIN_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, min: %zu, max: %zu",
>> + __func__, inode->i_ino, fi->i_inline_xattr_size,
>> + MIN_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;
>>
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index 42eb5c86330a..9184b7524c03 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -835,12 +835,9 @@ static int parse_options(struct super_block *sb, char *options)
>> return -EINVAL;
>> }
>> if (F2FS_OPTION(sbi).inline_xattr_size <
>> - sizeof(struct f2fs_xattr_header) / sizeof(__le32) ||
>> + MIN_INLINE_XATTR_SIZE ||
>> F2FS_OPTION(sbi).inline_xattr_size >
>> - DEF_ADDRS_PER_INODE -
>> - F2FS_TOTAL_EXTRA_ATTR_SIZE / sizeof(__le32) -
>> - DEF_INLINE_RESERVED_SIZE -
>> - MIN_INLINE_DENTRY_SIZE / sizeof(__le32)) {
>> + MAX_INLINE_XATTR_SIZE) {
>> f2fs_msg(sb, KERN_ERR,
>> "inline xattr size is out of range");
>> return -EINVAL;
>> diff --git a/fs/f2fs/xattr.h b/fs/f2fs/xattr.h
>> index 67db134da0f5..94e8a5eeaae1 100644
>> --- a/fs/f2fs/xattr.h
>> +++ b/fs/f2fs/xattr.h
>> @@ -55,6 +55,8 @@ struct f2fs_xattr_entry {
>> #define XATTR_FIRST_ENTRY(ptr) (XATTR_ENTRY(XATTR_HDR(ptr) + 1))
>> #define XATTR_ROUND (3)
>>
>> +#define XATTR_HDR_SIZE (sizeof(struct f2fs_xattr_header))
>> +
>> #define XATTR_ALIGN(size) (((size) + XATTR_ROUND) & ~XATTR_ROUND)
>>
>> #define ENTRY_SIZE(entry) (XATTR_ALIGN(sizeof(struct f2fs_xattr_entry) + \
>> @@ -78,6 +80,13 @@ struct f2fs_xattr_entry {
>> sizeof(struct f2fs_xattr_header) - \
>> sizeof(struct f2fs_xattr_entry))
>>
>> +#define MAX_INLINE_XATTR_SIZE (XATTR_HDR_SIZE / sizeof(__le32))
>
> I think this should be MIN_INLINE_XATTR_SIZE.
>
>> +#define MIN_INLINE_XATTR_SIZE \
>> + (DEF_ADDRS_PER_INODE - \
>> + F2FS_TOTAL_EXTRA_ATTR_SIZE / sizeof(__le32) - \
>> + DEF_INLINE_RESERVED_SIZE - \
>> + MIN_INLINE_DENTRY_SIZE / sizeof(__le32))
>> +
>
> And this should be MAX_INLINE_XATTR_SIZE.
Thanks for your reminding. :)
I should have missed to check something during testing this patch with
original corrupted image from bugzilla, sorry.
BTW, MIN_INLINE_XATTR_SIZE may be not necessary...
Thanks,
>
> Thanks,
> Sahitya.
>
>> /*
>> * On-disk structure of f2fs_xattr
>> * We use inline xattrs space + 1 block for xattr.
>> --
>> 2.18.0.rc1
>>
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@...ts.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
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