Re: Slab out of bounds in setxattr
Sorry, Sent the same thing twice. Here is the updated one. On Mon, Jun 4, 2018 at 1:22 PM, shankarapailoor wrote: > Hi Dave, > > I've updated the patch accordingly. > > Regards, > Shankara > > On Mon, Jun 4, 2018 at 11:39 AM, Dave Kleikamp > wrote: >> On 06/04/2018 01:30 PM, shankarapailoor wrote: >>> Hi Dave, >>> >>> Attached is my proposed patch. It solves the problem as you suggest >>> and I don't see the KASAN complaint. >> >> That looks good to me. Add a description and a Signed-off-by: and I'll >> get it pushed upstream. >> >> Thanks for finding this. >> >> Shaggy >> >>> >>> Regards, >>> Shankara >>> >>> On Mon, Jun 4, 2018 at 11:24 AM, Dave Kleikamp >>> wrote: On 06/01/2018 11:06 PM, shankarapailoor wrote: > Hi, > > Looking at the crash some more, it seems that if value_len > PAGE_SIZE > then e_buf->max_size is rounded up nearest page size [1]. If a new > attribute is added with value_len < e_buf->max_size - EA_SIZE(ea) then > no new space is allocated for the attiribute list [2] and this > triggers the KASAN slab out of bounds error. This is the case in the C > repro I provided. I see the problem. It looks like we should be calculating max_size earlier and using that to call kmalloc(). (xattr.c#496) Shaggy > > > 1. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L501 > 2. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L723 > > On Fri, Jun 1, 2018 at 1:52 PM, shankarapailoor > wrote: >> Hi Dave et al, >> >> I have been fuzzing linux 4.17-rc4 with JFS using Syzkaller KASAN: >> slab-out-of-bounds in jfs_xattr. >> >> Attached are my kernel configs and a C reproducer. In the first >> setxattr call it appears that length is much larger than the name. In >> __jfs_setxattr, I don't see where the length is checked against the >> actual value length. >> >> Regards, >> Shankara Pailoor > > > > -- > Regards, > Shankara Pailoor -- Regards, Shankara Pailoor jfspatch Description: Binary data
Re: Slab out of bounds in setxattr
Hi Dave, I've updated the patch accordingly. Regards, Shankara On Mon, Jun 4, 2018 at 11:39 AM, Dave Kleikamp wrote: > On 06/04/2018 01:30 PM, shankarapailoor wrote: >> Hi Dave, >> >> Attached is my proposed patch. It solves the problem as you suggest >> and I don't see the KASAN complaint. > > That looks good to me. Add a description and a Signed-off-by: and I'll > get it pushed upstream. > > Thanks for finding this. > > Shaggy > >> >> Regards, >> Shankara >> >> On Mon, Jun 4, 2018 at 11:24 AM, Dave Kleikamp >> wrote: >>> On 06/01/2018 11:06 PM, shankarapailoor wrote: Hi, Looking at the crash some more, it seems that if value_len > PAGE_SIZE then e_buf->max_size is rounded up nearest page size [1]. If a new attribute is added with value_len < e_buf->max_size - EA_SIZE(ea) then no new space is allocated for the attiribute list [2] and this triggers the KASAN slab out of bounds error. This is the case in the C repro I provided. >>> >>> I see the problem. It looks like we should be calculating max_size >>> earlier and using that to call kmalloc(). (xattr.c#496) >>> >>> Shaggy 1. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L501 2. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L723 On Fri, Jun 1, 2018 at 1:52 PM, shankarapailoor wrote: > Hi Dave et al, > > I have been fuzzing linux 4.17-rc4 with JFS using Syzkaller KASAN: > slab-out-of-bounds in jfs_xattr. > > Attached are my kernel configs and a C reproducer. In the first > setxattr call it appears that length is much larger than the name. In > __jfs_setxattr, I don't see where the length is checked against the > actual value length. > > Regards, > Shankara Pailoor -- Regards, Shankara Pailoor jfspatch Description: Binary data
Re: Slab out of bounds in setxattr
On 06/04/2018 01:30 PM, shankarapailoor wrote: > Hi Dave, > > Attached is my proposed patch. It solves the problem as you suggest > and I don't see the KASAN complaint. That looks good to me. Add a description and a Signed-off-by: and I'll get it pushed upstream. Thanks for finding this. Shaggy > > Regards, > Shankara > > On Mon, Jun 4, 2018 at 11:24 AM, Dave Kleikamp > wrote: >> On 06/01/2018 11:06 PM, shankarapailoor wrote: >>> Hi, >>> >>> Looking at the crash some more, it seems that if value_len > PAGE_SIZE >>> then e_buf->max_size is rounded up nearest page size [1]. If a new >>> attribute is added with value_len < e_buf->max_size - EA_SIZE(ea) then >>> no new space is allocated for the attiribute list [2] and this >>> triggers the KASAN slab out of bounds error. This is the case in the C >>> repro I provided. >> >> I see the problem. It looks like we should be calculating max_size >> earlier and using that to call kmalloc(). (xattr.c#496) >> >> Shaggy >>> >>> >>> 1. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L501 >>> 2. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L723 >>> >>> On Fri, Jun 1, 2018 at 1:52 PM, shankarapailoor >>> wrote: Hi Dave et al, I have been fuzzing linux 4.17-rc4 with JFS using Syzkaller KASAN: slab-out-of-bounds in jfs_xattr. Attached are my kernel configs and a C reproducer. In the first setxattr call it appears that length is much larger than the name. In __jfs_setxattr, I don't see where the length is checked against the actual value length. Regards, Shankara Pailoor
Re: Slab out of bounds in setxattr
Hi Dave, Attached is my proposed patch. It solves the problem as you suggest and I don't see the KASAN complaint. Regards, Shankara On Mon, Jun 4, 2018 at 11:24 AM, Dave Kleikamp wrote: > On 06/01/2018 11:06 PM, shankarapailoor wrote: >> Hi, >> >> Looking at the crash some more, it seems that if value_len > PAGE_SIZE >> then e_buf->max_size is rounded up nearest page size [1]. If a new >> attribute is added with value_len < e_buf->max_size - EA_SIZE(ea) then >> no new space is allocated for the attiribute list [2] and this >> triggers the KASAN slab out of bounds error. This is the case in the C >> repro I provided. > > I see the problem. It looks like we should be calculating max_size > earlier and using that to call kmalloc(). (xattr.c#496) > > Shaggy >> >> >> 1. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L501 >> 2. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L723 >> >> On Fri, Jun 1, 2018 at 1:52 PM, shankarapailoor >> wrote: >>> Hi Dave et al, >>> >>> I have been fuzzing linux 4.17-rc4 with JFS using Syzkaller KASAN: >>> slab-out-of-bounds in jfs_xattr. >>> >>> Attached are my kernel configs and a C reproducer. In the first >>> setxattr call it appears that length is much larger than the name. In >>> __jfs_setxattr, I don't see where the length is checked against the >>> actual value length. >>> >>> Regards, >>> Shankara Pailoor >> >> >> -- Regards, Shankara Pailoor jfspatch Description: Binary data
Re: Slab out of bounds in setxattr
On 06/01/2018 11:06 PM, shankarapailoor wrote: > Hi, > > Looking at the crash some more, it seems that if value_len > PAGE_SIZE > then e_buf->max_size is rounded up nearest page size [1]. If a new > attribute is added with value_len < e_buf->max_size - EA_SIZE(ea) then > no new space is allocated for the attiribute list [2] and this > triggers the KASAN slab out of bounds error. This is the case in the C > repro I provided. I see the problem. It looks like we should be calculating max_size earlier and using that to call kmalloc(). (xattr.c#496) Shaggy > > > 1. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L501 > 2. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L723 > > On Fri, Jun 1, 2018 at 1:52 PM, shankarapailoor > wrote: >> Hi Dave et al, >> >> I have been fuzzing linux 4.17-rc4 with JFS using Syzkaller KASAN: >> slab-out-of-bounds in jfs_xattr. >> >> Attached are my kernel configs and a C reproducer. In the first >> setxattr call it appears that length is much larger than the name. In >> __jfs_setxattr, I don't see where the length is checked against the >> actual value length. >> >> Regards, >> Shankara Pailoor > > >
Re: Slab out of bounds in setxattr
Hi, Looking at the crash some more, it seems that if value_len > PAGE_SIZE then e_buf->max_size is rounded up nearest page size [1]. If a new attribute is added with value_len < e_buf->max_size - EA_SIZE(ea) then no new space is allocated for the attiribute list [2] and this triggers the KASAN slab out of bounds error. This is the case in the C repro I provided. 1. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L501 2. https://elixir.bootlin.com/linux/v4.17-rc7/source/fs/jfs/xattr.c#L723 On Fri, Jun 1, 2018 at 1:52 PM, shankarapailoor wrote: > Hi Dave et al, > > I have been fuzzing linux 4.17-rc4 with JFS using Syzkaller KASAN: > slab-out-of-bounds in jfs_xattr. > > Attached are my kernel configs and a C reproducer. In the first > setxattr call it appears that length is much larger than the name. In > __jfs_setxattr, I don't see where the length is checked against the > actual value length. > > Regards, > Shankara Pailoor -- Regards, Shankara Pailoor
