Messages in this thread | | | Date | Thu, 27 Oct 2022 17:18:29 -0500 | Subject | Re: [PATCH] jfs: Fix fortify moan in symlink | From | Dave Kleikamp <> |
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Applied.
Thanks, Shaggy
On 10/24/22 1:49PM, Dr. David Alan Gilbert wrote: > * Kees Cook (keescook@chromium.org) wrote: >> On Sat, Oct 22, 2022 at 09:39:14PM +0100, linux@treblig.org wrote: >>> From: "Dr. David Alan Gilbert" <linux@treblig.org> >>> >>> JFS has in jfs_incore.h: >>> >>> /* _inline may overflow into _inline_ea when needed */ >>> /* _inline_ea may overlay the last part of >>> * file._xtroot if maxentry = XTROOTINITSLOT >>> */ >>> union { >>> struct { >>> /* 128: inline symlink */ >>> unchar _inline[128]; >>> /* 128: inline extended attr */ >>> unchar _inline_ea[128]; >>> }; >>> unchar _inline_all[256]; >>> >>> and currently the symlink code copies into _inline; >>> if this is larger than 128 bytes it triggers a fortify warning of the >>> form: >>> >>> memcpy: detected field-spanning write (size 132) of single field >>> "ip->i_link" at fs/jfs/namei.c:950 (size 18446744073709551615) >> >> Which compiler are you using for this build? > > I think that report was the same on gcc on Fedora 37 and whatever > syzkaller was running. > >> This size report (SIZE_MAX) >> should be impossible to reach. But also, the size is just wrong -- >> i_inline is 128 bytes, not SIZE_MAX. So, the detection is working >> (132 > 128), but the report is broken, and I can't see how... > > Yeh, and led me down a blind alley for a while thinking something had > really managed to screwup the strlen somehow. > >> >>> >>> when it's actually OK. >>> >>> Copy it into _inline_all instead. >>> >>> Reported-by: syzbot+5fc38b2ddbbca7f5c680@syzkaller.appspotmail.com >>> Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org> >>> --- >>> fs/jfs/namei.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c >>> index 9db4f5789c0ec..4fbbf88435e69 100644 >>> --- a/fs/jfs/namei.c >>> +++ b/fs/jfs/namei.c >>> @@ -946,7 +946,7 @@ static int jfs_symlink(struct user_namespace *mnt_userns, struct inode *dip, >>> if (ssize <= IDATASIZE) { >>> ip->i_op = &jfs_fast_symlink_inode_operations; >>> >>> - ip->i_link = JFS_IP(ip)->i_inline; >>> + ip->i_link = JFS_IP(ip)->i_inline_all; >>> memcpy(ip->i_link, name, ssize); >>> ip->i_size = ssize - 1; >>> >> >> Regardless, the fix looks correct to me! >> >> Reviewed-by: Kees Cook <keescook@chromium.org> > > Thanks! > > Dave > >> -- >> Kees Cook
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