Re: [PATCH] nfsd: Fix oops when parsing a 0 length export

[J. Bruce Fields]

On Fri, Nov 18, 2011 at 12:14:49PM +0200, Sasha Levin wrote:
> expkey_parse() oopses when handling a 0 length export. This is easily
> triggerable from usermode by writing 0 bytes into
> '/proc/[proc id]/net/rpc/nfsd.fh/channel'.

Thanks--how did you run across this?

--b.

> 
> Below is the log:
> 
> [ 1402.286893] BUG: unable to handle kernel paging request at ffff880077c49fff
> [ 1402.287632] IP: [<ffffffff812b4b99>] expkey_parse+0x28/0x2e1
> [ 1402.287632] PGD 2206063 PUD 1fdfd067 PMD 1ffbc067 PTE 8000000077c49160
> [ 1402.287632] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [ 1402.287632] CPU 1
> [ 1402.287632] Pid: 20198, comm: trinity Not tainted 3.2.0-rc2-sasha-00058-gc65cd37 #6
> [ 1402.287632] RIP: 0010:[<ffffffff812b4b99>]  [<ffffffff812b4b99>] expkey_parse+0x28/0x2e1
> [ 1402.287632] RSP: 0018:ffff880077f0fd68  EFLAGS: 00010292
> [ 1402.287632] RAX: ffff880077c49fff RBX: 00000000ffffffea RCX: 0000000001043400
> [ 1402.287632] RDX: 0000000000000000 RSI: ffff880077c4a000 RDI: ffffffff82283de0
> [ 1402.287632] RBP: ffff880077f0fe18 R08: 0000000000000001 R09: ffff880000000000
> [ 1402.287632] R10: 0000000000000000 R11: 0000000000000001 R12: ffff880077c4a000
> [ 1402.287632] R13: ffffffff82283de0 R14: 0000000001043400 R15: ffffffff82283de0
> [ 1402.287632] FS:  00007f25fec3f700(0000) GS:ffff88007d400000(0000) knlGS:0000000000000000
> [ 1402.287632] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [ 1402.287632] CR2: ffff880077c49fff CR3: 0000000077e1d000 CR4: 00000000000406e0
> [ 1402.287632] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 1402.287632] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [ 1402.287632] Process trinity (pid: 20198, threadinfo ffff880077f0e000, task ffff880077db17b0)
> [ 1402.287632] Stack:
> [ 1402.287632]  ffff880077db17b0 ffff880077c4a000 ffff880077f0fdb8 ffffffff810b411e
> [ 1402.287632]  ffff880000000000 ffff880077db17b0 ffff880077c4a000 ffffffff82283de0
> [ 1402.287632]  0000000001043400 ffffffff82283de0 ffff880077f0fde8 ffffffff81111f63
> [ 1402.287632] Call Trace:
> [ 1402.287632]  [<ffffffff810b411e>] ? lock_release+0x1af/0x1bc
> [ 1402.287632]  [<ffffffff81111f63>] ? might_fault+0x97/0x9e
> [ 1402.287632]  [<ffffffff81111f1a>] ? might_fault+0x4e/0x9e
> [ 1402.287632]  [<ffffffff81a8bcf2>] cache_do_downcall+0x3e/0x4f
> [ 1402.287632]  [<ffffffff81a8c950>] cache_write.clone.16+0xbb/0x130
> [ 1402.287632]  [<ffffffff81a8c9df>] ? cache_write_pipefs+0x1a/0x1a
> [ 1402.287632]  [<ffffffff81a8c9f8>] cache_write_procfs+0x19/0x1b
> [ 1402.287632]  [<ffffffff8118dc54>] proc_reg_write+0x8e/0xad
> [ 1402.287632]  [<ffffffff8113fe81>] vfs_write+0xaa/0xfd
> [ 1402.287632]  [<ffffffff8114142d>] ? fget_light+0x35/0x9e
> [ 1402.287632]  [<ffffffff8113ff8b>] sys_write+0x48/0x6f
> [ 1402.287632]  [<ffffffff81bbdb92>] system_call_fastpath+0x16/0x1b
> [ 1402.287632] Code: c0 c9 c3 55 48 63 d2 48 89 e5 48 8d 44 32 ff 41 57 41 56 41 55 41 54 53 bb ea ff ff ff 48 81 ec 88 00 00 00 48 89 b5 58 ff ff ff
> [ 1402.287632]  38 0a 0f 85 89 02 00 00 c6 00 00 48 8b 3d 44 4a e5 01 48 85
> [ 1402.287632] RIP  [<ffffffff812b4b99>] expkey_parse+0x28/0x2e1
> [ 1402.287632]  RSP <ffff880077f0fd68>
> [ 1402.287632] CR2: ffff880077c49fff
> [ 1402.287632] ---[ end trace 368ef53ff773a5e3 ]---
> 
> Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
> Cc: Neil Brown <neilb@xxxxxxx>
> Cc: linux-nfs@xxxxxxxxxxxxxxx
> Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
> ---
>  fs/nfsd/export.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
> index 62f3b90..5f312ab 100644
> --- a/fs/nfsd/export.c
> +++ b/fs/nfsd/export.c
> @@ -87,7 +87,7 @@ static int expkey_parse(struct cache_detail *cd, char *mesg, int mlen)
>  	struct svc_expkey key;
>  	struct svc_expkey *ek = NULL;
>  
> -	if (mesg[mlen-1] != '\n')
> +	if (mlen < 1 || mesg[mlen-1] != '\n')
>  		return -EINVAL;
>  	mesg[mlen-1] = 0;
>  
> -- 
> 1.7.8.rc1
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/