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 <yuch...@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-de...@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.
