Patchwork filesystems: use has_capability_noaudit interface for reserved blocks checks

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Submitter Eric Paris
Date Nov. 11, 2008, 7:12 p.m.
Message ID <1226430769.3353.5.camel@localhost.localdomain>
Download mbox | patch
Permalink /patch/8178/
State New
Headers show

Comments

Eric Paris - Nov. 11, 2008, 7:12 p.m.
ext[2,3,4], ufs, and ubifs all check for  CAP_SYS_RESOURCE to determine
if they should allow reserved blocks to be used.  A process not having
this capability is not failing some security decision and should not be
audited.  Thus move to using has_capability_noaudit.

Signed-off-by: Eric Paris <eparis@redhat.com>
---

I would like to push this patch through the security tree (since that's
the only place the new cap_noaudit interface exists), but I'd like to
get an ACK from each subsystem maintainer.

 fs/ext2/balloc.c     |    2 +-
 fs/ext3/balloc.c     |    2 +-
 fs/ext4/balloc.c     |    2 +-
 fs/ubifs/budget.c    |    3 ++-
 fs/ufs/balloc.c      |    2 +-
 security/commoncap.c |    1 +
 security/security.c  |    1 +
 7 files changed, 8 insertions(+), 5 deletions(-)
Mingming Cao - Nov. 13, 2008, 12:19 a.m.
在 2008-11-11二的 14:12 -0500,Eric Paris写道:
> ext[2,3,4], ufs, and ubifs all check for  CAP_SYS_RESOURCE to determine
> if they should allow reserved blocks to be used.  A process not having
> this capability is not failing some security decision and should not be
> audited.  Thus move to using has_capability_noaudit.
> 
Looks fine to me.

Eric Sandeen has  mentioned earlier about the security audit issue with
ext4. We fixed it in ext4, with this it is even better.


Reviewed-by: Mingming Cao <cmm@us.ibm.com>
> Signed-off-by: Eric Paris <eparis@redhat.com>
> ---
> 
> I would like to push this patch through the security tree (since that's
> the only place the new cap_noaudit interface exists), but I'd like to
> get an ACK from each subsystem maintainer.
> 
>  fs/ext2/balloc.c     |    2 +-
>  fs/ext3/balloc.c     |    2 +-
>  fs/ext4/balloc.c     |    2 +-
>  fs/ubifs/budget.c    |    3 ++-
>  fs/ufs/balloc.c      |    2 +-
>  security/commoncap.c |    1 +
>  security/security.c  |    1 +
>  7 files changed, 8 insertions(+), 5 deletions(-)
> 
> 
> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
> index 6dac7ba..e06d96d 100644
> --- a/fs/ext2/balloc.c
> +++ b/fs/ext2/balloc.c
> @@ -1192,7 +1192,7 @@ static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
> 
>  	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
>  	root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
> -	if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
> +	if (free_blocks < root_blocks + 1 && !has_capability_noaudit(current, CAP_SYS_RESOURCE) &&
>  		sbi->s_resuid != current->fsuid &&
>  		(sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
>  		return 0;
> diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
> index f5b57a2..f224ee4 100644
> --- a/fs/ext3/balloc.c
> +++ b/fs/ext3/balloc.c
> @@ -1421,7 +1421,7 @@ static int ext3_has_free_blocks(struct ext3_sb_info *sbi)
> 
>  	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
>  	root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
> -	if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
> +	if (free_blocks < root_blocks + 1 && !has_capability_noaudit(current, CAP_SYS_RESOURCE) &&
>  		sbi->s_resuid != current->fsuid &&
>  		(sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
>  		return 0;
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index d2003cd..a7c7c52 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -626,7 +626,7 @@ int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
>  	/* Hm, nope.  Are (enough) root reserved blocks available? */
>  	if (sbi->s_resuid == current->fsuid ||
>  	    ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
> -	    capable(CAP_SYS_RESOURCE)) {
> +	    has_capability_noaudit(current, CAP_SYS_RESOURCE)) {
>  		if (free_blocks >= (nblocks + dirty_blocks))
>  			return 1;
>  	}
> diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
> index 1a4973e..d17b8b4 100644
> --- a/fs/ubifs/budget.c
> +++ b/fs/ubifs/budget.c
> @@ -32,6 +32,7 @@
> 
>  #include "ubifs.h"
>  #include <linux/writeback.h>
> +#include <linux/capability.h>
>  #include <asm/div64.h>
> 
>  /*
> @@ -363,7 +364,7 @@ long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs)
>   */
>  static int can_use_rp(struct ubifs_info *c)
>  {
> -	if (current->fsuid == c->rp_uid || capable(CAP_SYS_RESOURCE) ||
> +	if (current->fsuid == c->rp_uid || has_capability_noaudit(current, CAP_SYS_RESOURCE) ||
>  	    (c->rp_gid != 0 && in_group_p(c->rp_gid)))
>  		return 1;
>  	return 0;
> diff --git a/fs/ufs/balloc.c b/fs/ufs/balloc.c
> index 0d9ada1..ad4398b 100644
> --- a/fs/ufs/balloc.c
> +++ b/fs/ufs/balloc.c
> @@ -411,7 +411,7 @@ u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
>  	/*
>  	 * There is not enough space for user on the device
>  	 */
> -	if (!capable(CAP_SYS_RESOURCE) && ufs_freespace(uspi, UFS_MINFREE) <= 0) {
> +	if (!has_capability_noaudit(current, CAP_SYS_RESOURCE) && ufs_freespace(uspi, UFS_MINFREE) <= 0) {
>  		unlock_super (sb);
>  		UFSD("EXIT (FAILED)\n");
>  		return 0;
> diff --git a/security/commoncap.c b/security/commoncap.c
> index 73999f6..5401e77 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -55,6 +55,7 @@ int cap_capable(struct task_struct *tsk, int cap, int audit)
>  		return 0;
>  	return -EPERM;
>  }
> +EXPORT_SYMBOL(cap_capable);
> 
>  int cap_settime(struct timespec *ts, struct timezone *tz)
>  {
> diff --git a/security/security.c b/security/security.c
> index 346f21e..d061eb1 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -170,6 +170,7 @@ int security_capable_noaudit(struct task_struct *tsk, int cap)
>  {
>  	return security_ops->capable(tsk, cap, SECURITY_CAP_NOAUDIT);
>  }
> +EXPORT_SYMBOL(security_capable_noaudit);
> 
>  int security_acct(struct file *file)
>  {
> 
> 
> --
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Andrew Morton - Nov. 13, 2008, 10:53 p.m.
On Tue, 11 Nov 2008 14:12:49 -0500
Eric Paris <eparis@redhat.com> wrote:

> ext[2,3,4], ufs, and ubifs all check for  CAP_SYS_RESOURCE to determine
> if they should allow reserved blocks to be used.  A process not having
> this capability is not failing some security decision and should not be
> audited.  Thus move to using has_capability_noaudit.
> 
> Signed-off-by: Eric Paris <eparis@redhat.com>
> ---
> 
> I would like to push this patch through the security tree (since that's
> the only place the new cap_noaudit interface exists), but I'd like to
> get an ACK from each subsystem maintainer.

OK by me.

Whoever added has_capability_noaudit() forgot to document it, so the
difference between has_capability_noaudit() and has_capability() eludes
this reader.
Theodore Ts'o - Nov. 13, 2008, 11:07 p.m.
On Thu, Nov 13, 2008 at 02:53:16PM -0800, Andrew Morton wrote:
> On Tue, 11 Nov 2008 14:12:49 -0500
> Eric Paris <eparis@redhat.com> wrote:
> 
> > ext[2,3,4], ufs, and ubifs all check for  CAP_SYS_RESOURCE to determine
> > if they should allow reserved blocks to be used.  A process not having
> > this capability is not failing some security decision and should not be
> > audited.  Thus move to using has_capability_noaudit.
> > 
> > Signed-off-by: Eric Paris <eparis@redhat.com>
> > ---
> > 
> > I would like to push this patch through the security tree (since that's
> > the only place the new cap_noaudit interface exists), but I'd like to
> > get an ACK from each subsystem maintainer.

For ext4:

Acked-by: "Theodore Ts'o" <tytso@mit.edu>

						- Ted
Artem Bityutskiy - Nov. 14, 2008, 7:55 a.m.
Eric Paris wrote:
> ext[2,3,4], ufs, and ubifs all check for  CAP_SYS_RESOURCE to determine
> if they should allow reserved blocks to be used.  A process not having
> this capability is not failing some security decision and should not be
> audited.  Thus move to using has_capability_noaudit.
> 
> Signed-off-by: Eric Paris <eparis@redhat.com>
> ---

UBIFS part looks OK, as long as the whole idea of the patch is right, which
I have not checked, but assume it is.

The only question is are you sure exporting 'cap_capable()' is relevant
to this patch? You do not seem to call it directly.
Eric Paris - Nov. 14, 2008, 3:36 p.m.
On Fri, 2008-11-14 at 09:55 +0200, Artem Bityutskiy wrote:
> Eric Paris wrote:
> > ext[2,3,4], ufs, and ubifs all check for  CAP_SYS_RESOURCE to determine
> > if they should allow reserved blocks to be used.  A process not having
> > this capability is not failing some security decision and should not be
> > audited.  Thus move to using has_capability_noaudit.
> > 
> > Signed-off-by: Eric Paris <eparis@redhat.com>
> > ---
> 
> UBIFS part looks OK, as long as the whole idea of the patch is right, which
> I have not checked, but assume it is.
> 
> The only question is are you sure exporting 'cap_capable()' is relevant
> to this patch? You do not seem to call it directly.

After this change, modules call has_capability_noaudit() which is a
#define which turns this into modules calling
security_capable_noaudit().  You noticed this and decided it was correct
to make that export.  But when CONFIG_SECURITY is not set
security_capable_notaudit() is a static inline which calls
cap_capable().  See include/linux/security.h line 2832 in the linux-next
tree.  Now modules are calling cap_capable directly, thus the export.

-Eric

Patch

diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index 6dac7ba..e06d96d 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -1192,7 +1192,7 @@  static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
 
 	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
 	root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
-	if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
+	if (free_blocks < root_blocks + 1 && !has_capability_noaudit(current, CAP_SYS_RESOURCE) &&
 		sbi->s_resuid != current->fsuid &&
 		(sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
 		return 0;
diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index f5b57a2..f224ee4 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1421,7 +1421,7 @@  static int ext3_has_free_blocks(struct ext3_sb_info *sbi)
 
 	free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
 	root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
-	if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
+	if (free_blocks < root_blocks + 1 && !has_capability_noaudit(current, CAP_SYS_RESOURCE) &&
 		sbi->s_resuid != current->fsuid &&
 		(sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
 		return 0;
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index d2003cd..a7c7c52 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -626,7 +626,7 @@  int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
 	/* Hm, nope.  Are (enough) root reserved blocks available? */
 	if (sbi->s_resuid == current->fsuid ||
 	    ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
-	    capable(CAP_SYS_RESOURCE)) {
+	    has_capability_noaudit(current, CAP_SYS_RESOURCE)) {
 		if (free_blocks >= (nblocks + dirty_blocks))
 			return 1;
 	}
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index 1a4973e..d17b8b4 100644
--- a/fs/ubifs/budget.c
+++ b/fs/ubifs/budget.c
@@ -32,6 +32,7 @@ 
 
 #include "ubifs.h"
 #include <linux/writeback.h>
+#include <linux/capability.h>
 #include <asm/div64.h>
 
 /*
@@ -363,7 +364,7 @@  long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs)
  */
 static int can_use_rp(struct ubifs_info *c)
 {
-	if (current->fsuid == c->rp_uid || capable(CAP_SYS_RESOURCE) ||
+	if (current->fsuid == c->rp_uid || has_capability_noaudit(current, CAP_SYS_RESOURCE) ||
 	    (c->rp_gid != 0 && in_group_p(c->rp_gid)))
 		return 1;
 	return 0;
diff --git a/fs/ufs/balloc.c b/fs/ufs/balloc.c
index 0d9ada1..ad4398b 100644
--- a/fs/ufs/balloc.c
+++ b/fs/ufs/balloc.c
@@ -411,7 +411,7 @@  u64 ufs_new_fragments(struct inode *inode, void *p, u64 fragment,
 	/*
 	 * There is not enough space for user on the device
 	 */
-	if (!capable(CAP_SYS_RESOURCE) && ufs_freespace(uspi, UFS_MINFREE) <= 0) {
+	if (!has_capability_noaudit(current, CAP_SYS_RESOURCE) && ufs_freespace(uspi, UFS_MINFREE) <= 0) {
 		unlock_super (sb);
 		UFSD("EXIT (FAILED)\n");
 		return 0;
diff --git a/security/commoncap.c b/security/commoncap.c
index 73999f6..5401e77 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -55,6 +55,7 @@  int cap_capable(struct task_struct *tsk, int cap, int audit)
 		return 0;
 	return -EPERM;
 }
+EXPORT_SYMBOL(cap_capable);
 
 int cap_settime(struct timespec *ts, struct timezone *tz)
 {
diff --git a/security/security.c b/security/security.c
index 346f21e..d061eb1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -170,6 +170,7 @@  int security_capable_noaudit(struct task_struct *tsk, int cap)
 {
 	return security_ops->capable(tsk, cap, SECURITY_CAP_NOAUDIT);
 }
+EXPORT_SYMBOL(security_capable_noaudit);
 
 int security_acct(struct file *file)
 {