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

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

[Sasha Levin]

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'.

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@fieldses.org>
Cc: Neil Brown <neilb@suse.de>
Cc: linux-nfs@vger.kernel.org
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 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

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@fieldses.org>
> Cc: Neil Brown <neilb@suse.de>
> Cc: linux-nfs@vger.kernel.org
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> ---
>  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@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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

[Sasha Levin]

On Tue, 2011-11-22 at 15:28 -0500, J. Bruce Fields wrote:
> 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.

Tried running a fuzzer on the system.

-- 

Sasha.

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

[J. Bruce Fields]

On Tue, Nov 22, 2011 at 10:33:29PM +0200, Sasha Levin wrote:
> On Tue, 2011-11-22 at 15:28 -0500, J. Bruce Fields wrote:
> > 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.
> 
> Tried running a fuzzer on the system.

OK, thanks.  As far as I can tell this could only be hit by a privileged
user doing something stupid.  And the bug has been there forever.

So I'm inclined just to queue this up for 3.3.

--b.

[patch] nfsd: oopses in cache_parse()

[Dan Carpenter]

[-- Attachment #1: Type: text/plain, Size: 1867 bytes --]

We fixed expkey_parse() in b2ea70afad "nfsd: Fix oops when parsing a
0 length export" but there are other cache_parse() implimentations
which have the same issue.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
Since half of the implimentations get this wrong, maybe we should
just check for this in cache_do_downcall().  Is there ever a valid
reason to pass a zero length string to cache_parse()?

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index cf8a6bd..1d147a8 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -496,7 +496,7 @@ static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
 	struct svc_export exp = {}, *expp;
 	int an_int;
 
-	if (mesg[mlen-1] != '\n')
+	if (mlen < 1 || mesg[mlen - 1] != '\n')
 		return -EINVAL;
 	mesg[mlen-1] = 0;
 
diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index a6e711a..d945d71 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -217,7 +217,7 @@ static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
 	ssize_t len;
 	int ret = -EINVAL;
 
-	if (buf[buflen-1] != '\n')
+	if (buflen < 1 || buf[buflen - 1] != '\n')
 		goto out;
 	buf[buflen-1] = '\0';
 
diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
index 9409627..f8456a4 100644
--- a/fs/nfsd/nfs4idmap.c
+++ b/fs/nfsd/nfs4idmap.c
@@ -202,7 +202,7 @@ idtoname_parse(struct cache_detail *cd, char *buf, int buflen)
 	int len;
 	int error = -EINVAL;
 
-	if (buf[buflen - 1] != '\n')
+	if (buflen < 1 || buf[buflen - 1] != '\n')
 		return (-EINVAL);
 	buf[buflen - 1]= '\0';
 
@@ -378,7 +378,7 @@ nametoid_parse(struct cache_detail *cd, char *buf, int buflen)
 	char *buf1;
 	int error = -EINVAL;
 
-	if (buf[buflen - 1] != '\n')
+	if (buflen < 1 || buf[buflen - 1] != '\n')
 		return (-EINVAL);
 	buf[buflen - 1]= '\0';
 


[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [patch] nfsd: oopses in cache_parse()

[J. Bruce Fields]

On Mon, Jan 16, 2012 at 02:52:58PM +0300, Dan Carpenter wrote:
> We fixed expkey_parse() in b2ea70afad "nfsd: Fix oops when parsing a
> 0 length export" but there are other cache_parse() implimentations
> which have the same issue.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> Since half of the implimentations get this wrong, maybe we should
> just check for this in cache_do_downcall().  Is there ever a valid
> reason to pass a zero length string to cache_parse()?

I don't think so, no.  Checking in cache_do_downcall() sounds like a
good idea.

--b.

> 
> diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
> index cf8a6bd..1d147a8 100644
> --- a/fs/nfsd/export.c
> +++ b/fs/nfsd/export.c
> @@ -496,7 +496,7 @@ static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
>  	struct svc_export exp = {}, *expp;
>  	int an_int;
>  
> -	if (mesg[mlen-1] != '\n')
> +	if (mlen < 1 || mesg[mlen - 1] != '\n')
>  		return -EINVAL;
>  	mesg[mlen-1] = 0;
>  
> diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> index a6e711a..d945d71 100644
> --- a/fs/nfs/dns_resolve.c
> +++ b/fs/nfs/dns_resolve.c
> @@ -217,7 +217,7 @@ static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
>  	ssize_t len;
>  	int ret = -EINVAL;
>  
> -	if (buf[buflen-1] != '\n')
> +	if (buflen < 1 || buf[buflen - 1] != '\n')
>  		goto out;
>  	buf[buflen-1] = '\0';
>  
> diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
> index 9409627..f8456a4 100644
> --- a/fs/nfsd/nfs4idmap.c
> +++ b/fs/nfsd/nfs4idmap.c
> @@ -202,7 +202,7 @@ idtoname_parse(struct cache_detail *cd, char *buf, int buflen)
>  	int len;
>  	int error = -EINVAL;
>  
> -	if (buf[buflen - 1] != '\n')
> +	if (buflen < 1 || buf[buflen - 1] != '\n')
>  		return (-EINVAL);
>  	buf[buflen - 1]= '\0';
>  
> @@ -378,7 +378,7 @@ nametoid_parse(struct cache_detail *cd, char *buf, int buflen)
>  	char *buf1;
>  	int error = -EINVAL;
>  
> -	if (buf[buflen - 1] != '\n')
> +	if (buflen < 1 || buf[buflen - 1] != '\n')
>  		return (-EINVAL);
>  	buf[buflen - 1]= '\0';
>  
> 

Re: [patch] nfsd: oopses in cache_parse()

[Dan Carpenter]

[-- Attachment #1: Type: text/plain, Size: 853 bytes --]

On Mon, Jan 16, 2012 at 10:50:31AM -0500, J. Bruce Fields wrote:
> On Mon, Jan 16, 2012 at 02:52:58PM +0300, Dan Carpenter wrote:
> > We fixed expkey_parse() in b2ea70afad "nfsd: Fix oops when parsing a
> > 0 length export" but there are other cache_parse() implimentations
> > which have the same issue.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> > Since half of the implimentations get this wrong, maybe we should
> > just check for this in cache_do_downcall().  Is there ever a valid
> > reason to pass a zero length string to cache_parse()?
> 
> I don't think so, no.  Checking in cache_do_downcall() sounds like a
> good idea.

Yeah.  I checked and none of the cache_parse() implementations do
anything with a zero length string.  Ignore that patch, I'll send
another.

regards,
dan carpenter


[-- Attachment #2: Digital signature --]
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[patch] nfsd: don't allow zero length strings in cache_parse()

[Dan Carpenter]

[-- Attachment #1: Type: text/plain, Size: 577 bytes --]

There is no point in passing a zero length string here and quite a
few of that cache_parse() implementations will Oops if count is
zero.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 465df9a..8c6598e 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -828,6 +828,8 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
 {
 	ssize_t ret;
 
+	if (count == 0)
+		return -EINVAL;
 	if (copy_from_user(kaddr, buf, count))
 		return -EFAULT;
 	kaddr[count] = '\0';

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [patch] nfsd: don't allow zero length strings in cache_parse()

[J. Bruce Fields]

On Wed, Jan 18, 2012 at 12:56:02PM +0300, Dan Carpenter wrote:
> There is no point in passing a zero length string here and quite a
> few of that cache_parse() implementations will Oops if count is
> zero.

Thanks, I'll apply.

Could we clean up any checks in cache_parse() that are unnecessary now?

--b.

> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index 465df9a..8c6598e 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -828,6 +828,8 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
>  {
>  	ssize_t ret;
>  
> +	if (count == 0)
> +		return -EINVAL;
>  	if (copy_from_user(kaddr, buf, count))
>  		return -EFAULT;
>  	kaddr[count] = '\0';

[patch] nfsd: remove some unneeded checks

[Dan Carpenter]

[-- Attachment #1: Type: text/plain, Size: 940 bytes --]

We check for zero length strings in the caller now, so these aren't
needed.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index cf8a6bd..8e9689a 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 (mlen < 1 || mesg[mlen-1] != '\n')
+	if (mesg[mlen - 1] != '\n')
 		return -EINVAL;
 	mesg[mlen-1] = 0;
 
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 01153ea..6ab3573 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -509,7 +509,7 @@ static int unix_gid_parse(struct cache_detail *cd,
 	time_t expiry;
 	struct unix_gid ug, *ugp;
 
-	if (mlen <= 0 || mesg[mlen-1] != '\n')
+	if (mesg[mlen - 1] != '\n')
 		return -EINVAL;
 	mesg[mlen-1] = 0;
 

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [patch] nfsd: remove some unneeded checks

[J. Bruce Fields]

On Fri, Jan 20, 2012 at 10:48:18AM +0300, Dan Carpenter wrote:
> We check for zero length strings in the caller now, so these aren't
> needed.

Thanks!  Applying.--b.

> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
> index cf8a6bd..8e9689a 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 (mlen < 1 || mesg[mlen-1] != '\n')
> +	if (mesg[mlen - 1] != '\n')
>  		return -EINVAL;
>  	mesg[mlen-1] = 0;
>  
> diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
> index 01153ea..6ab3573 100644
> --- a/net/sunrpc/svcauth_unix.c
> +++ b/net/sunrpc/svcauth_unix.c
> @@ -509,7 +509,7 @@ static int unix_gid_parse(struct cache_detail *cd,
>  	time_t expiry;
>  	struct unix_gid ug, *ugp;
>  
> -	if (mlen <= 0 || mesg[mlen-1] != '\n')
> +	if (mesg[mlen - 1] != '\n')
>  		return -EINVAL;
>  	mesg[mlen-1] = 0;
>