* [PATCH] evm: check for remount ro in progress before writing
@ 2018-03-01 12:38 Sascha Hauer
2018-03-08 21:42 ` Mimi Zohar
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Sascha Hauer @ 2018-03-01 12:38 UTC (permalink / raw)
To: linux-integrity; +Cc: Mimi Zohar, Sascha Hauer
EVM might update the evm xattr while the VFS performs a remount to
readonly mode. This is not properly checked for, additionally check
the s_readonly_remount superblock flag before writing.
The bug can for example be observed with UBIFS. UBIFS checks the free
space on the device before and after a remount. With EVM enabled the
free space sometimes differs between both checks.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
security/integrity/evm/evm_main.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index a8d502827270..4a147a998aa7 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -185,6 +185,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
iint->flags |= EVM_IMMUTABLE_DIGSIG;
evm_status = INTEGRITY_PASS_IMMUTABLE;
} else if (!IS_RDONLY(d_backing_inode(dentry)) &&
+ !(dentry->d_inode->i_sb->s_readonly_remount) &&
!IS_IMMUTABLE(d_backing_inode(dentry))) {
evm_update_evmxattr(dentry, xattr_name,
xattr_value,
--
2.16.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] evm: check for remount ro in progress before writing
2018-03-01 12:38 [PATCH] evm: check for remount ro in progress before writing Sascha Hauer
@ 2018-03-08 21:42 ` Mimi Zohar
2018-03-11 21:52 ` Mimi Zohar
2018-03-16 17:12 ` Mimi Zohar
2 siblings, 0 replies; 4+ messages in thread
From: Mimi Zohar @ 2018-03-08 21:42 UTC (permalink / raw)
To: Sascha Hauer, linux-integrity; +Cc: Matthew Garrett
On Thu, 2018-03-01 at 13:38 +0100, Sascha Hauer wrote:
> EVM might update the evm xattr while the VFS performs a remount to
> readonly mode. This is not properly checked for, additionally check
> the s_readonly_remount superblock flag before writing.
> The bug can for example be observed with UBIFS. UBIFS checks the free
> space on the device before and after a remount. With EVM enabled the
> free space sometimes differs between both checks.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> security/integrity/evm/evm_main.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index a8d502827270..4a147a998aa7 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -185,6 +185,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
> iint->flags |= EVM_IMMUTABLE_DIGSIG;
> evm_status = INTEGRITY_PASS_IMMUTABLE;
> } else if (!IS_RDONLY(d_backing_inode(dentry)) &&
> + !(dentry->d_inode->i_sb->s_readonly_remount) &&
> !IS_IMMUTABLE(d_backing_inode(dentry))) {
> evm_update_evmxattr(dentry, xattr_name,
> xattr_value,
Mathew's EVM Portable signature patch should have inverted the (!rc)
test, but didn't. With this patch, there's now a checkpatch over 80
character line warning.
Mimi
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] evm: check for remount ro in progress before writing
2018-03-01 12:38 [PATCH] evm: check for remount ro in progress before writing Sascha Hauer
2018-03-08 21:42 ` Mimi Zohar
@ 2018-03-11 21:52 ` Mimi Zohar
2018-03-16 17:12 ` Mimi Zohar
2 siblings, 0 replies; 4+ messages in thread
From: Mimi Zohar @ 2018-03-11 21:52 UTC (permalink / raw)
To: Sascha Hauer, linux-integrity
On Thu, 2018-03-01 at 13:38 +0100, Sascha Hauer wrote:
> EVM might update the evm xattr while the VFS performs a remount to
> readonly mode. This is not properly checked for, additionally check
> the s_readonly_remount superblock flag before writing.
> The bug can for example be observed with UBIFS. UBIFS checks the free
> space on the device before and after a remount. With EVM enabled the
> free space sometimes differs between both checks.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> security/integrity/evm/evm_main.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index a8d502827270..4a147a998aa7 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -185,6 +185,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
> iint->flags |= EVM_IMMUTABLE_DIGSIG;
> evm_status = INTEGRITY_PASS_IMMUTABLE;
> } else if (!IS_RDONLY(d_backing_inode(dentry)) &&
> + !(dentry->d_inode->i_sb->s_readonly_remount) &&
The other 2 conditions are using d_back_inode(). Shouldn't this one
be too?
Mimi
> !IS_IMMUTABLE(d_backing_inode(dentry))) {
> evm_update_evmxattr(dentry, xattr_name,
> xattr_value,
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] evm: check for remount ro in progress before writing
2018-03-01 12:38 [PATCH] evm: check for remount ro in progress before writing Sascha Hauer
2018-03-08 21:42 ` Mimi Zohar
2018-03-11 21:52 ` Mimi Zohar
@ 2018-03-16 17:12 ` Mimi Zohar
2 siblings, 0 replies; 4+ messages in thread
From: Mimi Zohar @ 2018-03-16 17:12 UTC (permalink / raw)
To: Sascha Hauer, linux-integrity
On Thu, 2018-03-01 at 13:38 +0100, Sascha Hauer wrote:
> EVM might update the evm xattr while the VFS performs a remount to
> readonly mode. This is not properly checked for, additionally check
> the s_readonly_remount superblock flag before writing.
> The bug can for example be observed with UBIFS. UBIFS checks the free
> space on the device before and after a remount. With EVM enabled the
> free space sometimes differs between both checks.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
I've modified the patch to use d_backing_inode() and fixed the
checkpatch over 80 character warning. It's now applied.
thanks!
Mimi
> ---
> security/integrity/evm/evm_main.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index a8d502827270..4a147a998aa7 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -185,6 +185,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
> iint->flags |= EVM_IMMUTABLE_DIGSIG;
> evm_status = INTEGRITY_PASS_IMMUTABLE;
> } else if (!IS_RDONLY(d_backing_inode(dentry)) &&
> + !(dentry->d_inode->i_sb->s_readonly_remount) &&
> !IS_IMMUTABLE(d_backing_inode(dentry))) {
> evm_update_evmxattr(dentry, xattr_name,
> xattr_value,
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-03-16 17:12 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2018-03-01 12:38 [PATCH] evm: check for remount ro in progress before writing Sascha Hauer
2018-03-08 21:42 ` Mimi Zohar
2018-03-11 21:52 ` Mimi Zohar
2018-03-16 17:12 ` Mimi Zohar
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