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UFS2: Fix DoS due to corrupted extattrfile

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Prior versions of FreeBSD (11.x) may have produced a corrupt extattr file.
(Specifically, r312416 accidentally fixed this defect by removing a strcpy.)
CURRENT FreeBSD supports disk images from those prior versions of FreeBSD.
Validate the internal structure as soon as we read it in from disk, to
prevent these extattr files from causing invariants violations and DoS.

Attempting to access the extattr portion of these files results in
EINTEGRITY.  At this time, the only way to repair files damaged in this way
is to copy the contents to another file and move it over the original.

PR:		244089
Reported by:	Andrea Venturoli <ml AT netfence.it>
Reviewed by:	kib
Discussed with:	mckusick (earlier draft)
Security:	no
Differential Revision:	https://reviews.freebsd.org/D27010
This commit is contained in:
Conrad Meyer 2020-10-30 19:00:42 +00:00
parent 3f3878075e
commit e6790841f7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=367181
2 changed files with 21 additions and 12 deletions
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31
sys/ufs/ffs/ffs_vnops.c
View file

@ -1200,9 +1200,8 @@ ffs_findextattr(u_char *ptr, u_int length, int nspace, const char *name,
eap = (struct extattr *)ptr;
eaend = (struct extattr *)(ptr + length);
for (; eap < eaend; eap = EXTATTR_NEXT(eap)) {
/* make sure this entry is complete */
if (EXTATTR_NEXT(eap) > eaend)
break;
KASSERT(EXTATTR_NEXT(eap) <= eaend,
("extattr next %p beyond %p", EXTATTR_NEXT(eap), eaend));
if (eap->ea_namespace != nspace || eap->ea_namelength != nlen
|| memcmp(eap->ea_name, name, nlen) != 0)
continue;
@ -1216,8 +1215,9 @@ ffs_findextattr(u_char *ptr, u_int length, int nspace, const char *name,
}
static int
ffs_rdextattr(u_char **p, struct vnode *vp, struct thread *td, int extra)
ffs_rdextattr(u_char **p, struct vnode *vp, struct thread *td)
{
const struct extattr *eap, *eaend, *eapnext;
struct inode *ip;
struct ufs2_dinode *dp;
struct fs *fs;
@ -1231,10 +1231,10 @@ ffs_rdextattr(u_char **p, struct vnode *vp, struct thread *td, int extra)
fs = ITOFS(ip);
dp = ip->i_din2;
easize = dp->di_extsize;
if ((uoff_t)easize + extra > UFS_NXADDR * fs->fs_bsize)
if ((uoff_t)easize > UFS_NXADDR * fs->fs_bsize)
return (EFBIG);
eae = malloc(easize + extra, M_TEMP, M_WAITOK);
eae = malloc(easize, M_TEMP, M_WAITOK);
liovec.iov_base = eae;
liovec.iov_len = easize;
@ -1249,7 +1249,17 @@ ffs_rdextattr(u_char **p, struct vnode *vp, struct thread *td, int extra)
error = ffs_extread(vp, &luio, IO_EXT | IO_SYNC);
if (error) {
free(eae, M_TEMP);
return(error);
return (error);
}
/* Validate disk xattrfile contents. */
for (eap = (void *)eae, eaend = (void *)(eae + easize); eap < eaend;
eap = eapnext) {
eapnext = EXTATTR_NEXT(eap);
/* Bogusly short entry or bogusly long entry. */
if (eap->ea_length < sizeof(*eap) || eapnext > eaend) {
free(eae, M_TEMP);
return (EINTEGRITY);
}
}
*p = eae;
return (0);
@ -1300,7 +1310,7 @@ ffs_open_ea(struct vnode *vp, struct ucred *cred, struct thread *td)
return (0);
}
dp = ip->i_din2;
error = ffs_rdextattr(&ip->i_ea_area, vp, td, 0);
error = ffs_rdextattr(&ip->i_ea_area, vp, td);
if (error) {
ffs_unlock_ea(vp);
return (error);
@ -1606,9 +1616,8 @@ vop_listextattr {
eap = (struct extattr *)ip->i_ea_area;
eaend = (struct extattr *)(ip->i_ea_area + ip->i_ea_len);
for (; error == 0 && eap < eaend; eap = EXTATTR_NEXT(eap)) {
/* make sure this entry is complete */
if (EXTATTR_NEXT(eap) > eaend)
break;
KASSERT(EXTATTR_NEXT(eap) <= eaend,
("extattr next %p beyond %p", EXTATTR_NEXT(eap), eaend));
if (eap->ea_namespace != ap->a_attrnamespace)
continue;

2
sys/ufs/ufs/extattr.h
View file

@ -95,7 +95,7 @@ struct extattr {
* content referenced by eap.
*/
#define EXTATTR_NEXT(eap) \
((struct extattr *)(((u_char *)(eap)) + (eap)->ea_length))
((struct extattr *)(__DECONST(char *, (eap)) + (eap)->ea_length))
#define EXTATTR_CONTENT(eap) \
(void *)(((u_char *)(eap)) + EXTATTR_BASE_LENGTH(eap))
#define EXTATTR_CONTENT_SIZE(eap) \