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SubjectRe: [f2fs-dev] [PATCH] f2fs: fix to do sanity check with inode.i_inline_xattr_size
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@huawei.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,
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@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

--
--
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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