Messages in this thread Patch in this message | | | Date | Tue, 9 May 2017 17:03:50 -0400 | From | "J . Bruce Fields" <> | Subject | Re: [PATCH] nfsd: avoid out of bounds read on array nfsd4_layout_ops |
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On Tue, May 09, 2017 at 05:04:14PM +0300, Dan Carpenter wrote: > On Tue, May 09, 2017 at 02:31:21PM +0100, Colin King wrote: > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > > index 1dbf62190bee..c453a1998e00 100644 > > --- a/fs/nfsd/nfs4proc.c > > +++ b/fs/nfsd/nfs4proc.c > > @@ -1259,7 +1259,8 @@ nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type) > > return NULL; > > } > > > > - if (layout_type >= 32 || !(exp->ex_layout_types & (1 << layout_type))) { > > + if (layout_type >= LAYOUT_TYPE_MAX || > > + !(exp->ex_layout_types & (1 << layout_type))) { > > The 32 is there to prevent a shift wrapping bug. The bit test prevents > a buffer overflow so this can't actually overflow.
Yes, looks like a false positive for coverity.
> But this change doesn't hurt and is probably cleaner.
Sure. Hope it's OK if I just merge this into the previous commit:
--b.
commit 16b6f81d8ed9 Author: Ari Kauppi <ari@synopsys.com> Date: Fri May 5 16:07:55 2017 -0400
nfsd: fix undefined behavior in nfsd4_layout_verify
UBSAN: Undefined behaviour in fs/nfsd/nfs4proc.c:1262:34 shift exponent 128 is too large for 32-bit type 'int'
Depending on compiler+architecture, this may cause the check for layout_type to succeed for overly large values (which seems to be the case with amd64). The large value will be later used in de-referencing nfsd4_layout_ops for function pointers.
Reported-by: Jani Tuovila <tuovila@synopsys.com> Signed-off-by: Ari Kauppi <ari@synopsys.com> [colin.king@canonical.com: use LAYOUT_TYPE_MAX instead of 32] Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index d86031b6ad79..c453a1998e00 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1259,7 +1259,8 @@ nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type) return NULL; } - if (!(exp->ex_layout_types & (1 << layout_type))) { + if (layout_type >= LAYOUT_TYPE_MAX || + !(exp->ex_layout_types & (1 << layout_type))) { dprintk("%s: layout type %d not supported\n", __func__, layout_type); return NULL;
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