[PATCH] NFSD: correctly range-check v4.x minor version when setting versions.

[PATCH] NFSD: correctly range-check v4.x minor version when setting versions.

[NeilBrown]

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Writing to /proc/fs/nfsd/versions allows individual major versions
and NFSv4 minor versions to be enabled or disabled.

However NFSv4.0 cannot currently be disabled, thought there is no good reason.
Also the minor number is parsed as a 'long' but used as an 'int'
so '4294967297' will be incorrectly treated as '1'.

This patch removes the test on 'minor == 0' and switches to kstrtouint()
to get correct range checking.

When reading from /proc/fs/nfsd/versions, 4.0 is current not reported.
To allow the disabling for v4.0 to be visible, while maintaining
backward compatibility, change code to report "-4.0" if appropriate, but
not "+4.0".

Signed-off-by: NeilBrown <neilb@suse.com>
---
 fs/nfsd/nfsctl.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index f3b2f34b10a3..d54fb0e3f30e 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -569,8 +569,7 @@ static ssize_t __write_versions(struct file *file, char *buf, size_t size)
 			if (*minorp == '.') {
 				if (num != 4)
 					return -EINVAL;
-				minor = simple_strtoul(minorp+1, NULL, 0);
-				if (minor == 0)
+				if (kstrtouint(minorp+1, 0, &minor) < 0)
 					return -EINVAL;
 				if (nfsd_minorversion(minor, sign == '-' ?
 						     NFSD_CLEAR : NFSD_SET) < 0)
@@ -613,8 +612,13 @@ static ssize_t __write_versions(struct file *file, char *buf, size_t size)
 			tlen += len;
 		}
 	if (nfsd_vers(4, NFSD_AVAIL))
-		for (minor = 1; minor <= NFSD_SUPPORTED_MINOR_VERSION;
+		for (minor = 0; minor <= NFSD_SUPPORTED_MINOR_VERSION;
 		     minor++) {
+			if (minor == 0 && nfsd_minorversion(minor, NFSD_TEST))
+				/* for backward compatibility, don't report
+				 * +4.0
+				 */
+				continue;
 			len = snprintf(buf, remaining, " %c4.%u",
 					(nfsd_vers(4, NFSD_TEST) &&
 					 nfsd_minorversion(minor, NFSD_TEST)) ?
-- 
2.11.0


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Re: [PATCH] NFSD: correctly range-check v4.x minor version when setting versions.

[J. Bruce Fields]

Makes sense to me, queueing up for 4.11 (none of this seems urgent).

--b.

On Wed, Dec 21, 2016 at 02:32:19PM +1100, NeilBrown wrote:
> 
> Writing to /proc/fs/nfsd/versions allows individual major versions
> and NFSv4 minor versions to be enabled or disabled.
> 
> However NFSv4.0 cannot currently be disabled, thought there is no good reason.
> Also the minor number is parsed as a 'long' but used as an 'int'
> so '4294967297' will be incorrectly treated as '1'.
> 
> This patch removes the test on 'minor == 0' and switches to kstrtouint()
> to get correct range checking.
> 
> When reading from /proc/fs/nfsd/versions, 4.0 is current not reported.
> To allow the disabling for v4.0 to be visible, while maintaining
> backward compatibility, change code to report "-4.0" if appropriate, but
> not "+4.0".
> 
> Signed-off-by: NeilBrown <neilb@suse.com>
> ---
>  fs/nfsd/nfsctl.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index f3b2f34b10a3..d54fb0e3f30e 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -569,8 +569,7 @@ static ssize_t __write_versions(struct file *file, char *buf, size_t size)
>  			if (*minorp == '.') {
>  				if (num != 4)
>  					return -EINVAL;
> -				minor = simple_strtoul(minorp+1, NULL, 0);
> -				if (minor == 0)
> +				if (kstrtouint(minorp+1, 0, &minor) < 0)
>  					return -EINVAL;
>  				if (nfsd_minorversion(minor, sign == '-' ?
>  						     NFSD_CLEAR : NFSD_SET) < 0)
> @@ -613,8 +612,13 @@ static ssize_t __write_versions(struct file *file, char *buf, size_t size)
>  			tlen += len;
>  		}
>  	if (nfsd_vers(4, NFSD_AVAIL))
> -		for (minor = 1; minor <= NFSD_SUPPORTED_MINOR_VERSION;
> +		for (minor = 0; minor <= NFSD_SUPPORTED_MINOR_VERSION;
>  		     minor++) {
> +			if (minor == 0 && nfsd_minorversion(minor, NFSD_TEST))
> +				/* for backward compatibility, don't report
> +				 * +4.0
> +				 */
> +				continue;
>  			len = snprintf(buf, remaining, " %c4.%u",
>  					(nfsd_vers(4, NFSD_TEST) &&
>  					 nfsd_minorversion(minor, NFSD_TEST)) ?
> -- 
> 2.11.0
> 

Re: [PATCH] NFSD: correctly range-check v4.x minor version when setting versions.

[NeilBrown]

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On Thu, Dec 22 2016, J. Bruce Fields wrote:
> Makes sense to me, queueing up for 4.11 (none of this seems urgent).
>

Thanks!  It's a while since I've seen a *less* urgent patch :-)

NeilBrown

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