> From: Casey Schaufler [mailto:casey@xxxxxxxxxxxxxxxx] > Sent: Wednesday, April 7, 2021 6:18 PM > On 4/7/2021 3:52 AM, Roberto Sassu wrote: > > ima_inode_setxattr() and ima_inode_removexattr() hooks are called > before an > > operation is performed. Thus, ima_reset_appraise_flags() should not be > > called there, as flags might be unnecessarily reset if the operation is > > denied. > > > > This patch introduces the post hooks ima_inode_post_setxattr() and > > ima_inode_post_removexattr(), and adds the call to > > ima_reset_appraise_flags() in the new functions. > > > > Cc: Casey Schaufler <casey@xxxxxxxxxxxxxxxx> > > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> > > --- > > fs/xattr.c | 2 ++ > > include/linux/ima.h | 18 ++++++++++++++++++ > > security/integrity/ima/ima_appraise.c | 25 ++++++++++++++++++++++-- > - > > security/security.c | 1 + > > 4 files changed, 43 insertions(+), 3 deletions(-) > > > > diff --git a/fs/xattr.c b/fs/xattr.c > > index b3444e06cded..81847f132d26 100644 > > --- a/fs/xattr.c > > +++ b/fs/xattr.c > > @@ -16,6 +16,7 @@ > > #include <linux/namei.h> > > #include <linux/security.h> > > #include <linux/evm.h> > > +#include <linux/ima.h> > > #include <linux/syscalls.h> > > #include <linux/export.h> > > #include <linux/fsnotify.h> > > @@ -502,6 +503,7 @@ __vfs_removexattr_locked(struct > user_namespace *mnt_userns, > > > > if (!error) { > > fsnotify_xattr(dentry); > > + ima_inode_post_removexattr(dentry, name); > > evm_inode_post_removexattr(dentry, name); > > } > > > > diff --git a/include/linux/ima.h b/include/linux/ima.h > > index 61d5723ec303..5e059da43857 100644 > > --- a/include/linux/ima.h > > +++ b/include/linux/ima.h > > @@ -171,7 +171,13 @@ extern void ima_inode_post_setattr(struct > user_namespace *mnt_userns, > > struct dentry *dentry); > > extern int ima_inode_setxattr(struct dentry *dentry, const char > *xattr_name, > > const void *xattr_value, size_t xattr_value_len); > > +extern void ima_inode_post_setxattr(struct dentry *dentry, > > + const char *xattr_name, > > + const void *xattr_value, > > + size_t xattr_value_len); > > extern int ima_inode_removexattr(struct dentry *dentry, const char > *xattr_name); > > +extern void ima_inode_post_removexattr(struct dentry *dentry, > > + const char *xattr_name); > > #else > > static inline bool is_ima_appraise_enabled(void) > > { > > @@ -192,11 +198,23 @@ static inline int ima_inode_setxattr(struct dentry > *dentry, > > return 0; > > } > > > > +static inline void ima_inode_post_setxattr(struct dentry *dentry, > > + const char *xattr_name, > > + const void *xattr_value, > > + size_t xattr_value_len) > > +{ > > +} > > + > > static inline int ima_inode_removexattr(struct dentry *dentry, > > const char *xattr_name) > > { > > return 0; > > } > > + > > +static inline void ima_inode_post_removexattr(struct dentry *dentry, > > + const char *xattr_name) > > +{ > > +} > > #endif /* CONFIG_IMA_APPRAISE */ > > > > #if defined(CONFIG_IMA_APPRAISE) && > defined(CONFIG_INTEGRITY_TRUSTED_KEYRING) > > diff --git a/security/integrity/ima/ima_appraise.c > b/security/integrity/ima/ima_appraise.c > > index 565e33ff19d0..1f029e4c8d7f 100644 > > --- a/security/integrity/ima/ima_appraise.c > > +++ b/security/integrity/ima/ima_appraise.c > > @@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, > const char *xattr_name, > > if (result == 1) { > > if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) > > return -EINVAL; > > - ima_reset_appraise_flags(d_backing_inode(dentry), > > - xvalue->type == EVM_IMA_XATTR_DIGSIG); > > result = 0; > > } > > return result; > > } > > > > +void ima_inode_post_setxattr(struct dentry *dentry, const char > *xattr_name, > > + const void *xattr_value, size_t xattr_value_len) > > +{ > > + const struct evm_ima_xattr_data *xvalue = xattr_value; > > + int result; > > + > > + result = ima_protect_xattr(dentry, xattr_name, xattr_value, > > + xattr_value_len); > > + if (result == 1) > > + ima_reset_appraise_flags(d_backing_inode(dentry), > > + xvalue->type == EVM_IMA_XATTR_DIGSIG); > > +} > > + > > Now you're calling ima_protect_xattr() twice for each setxattr. > Is that safe? Is it performant? Does it matter? Hi Casey I would expect that this does not have a significant impact on the performance (it is just a strcmp on the xattr name). Thanks Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli > > int ima_inode_removexattr(struct dentry *dentry, const char > *xattr_name) > > { > > int result; > > > > result = ima_protect_xattr(dentry, xattr_name, NULL, 0); > > if (result == 1) { > > - ima_reset_appraise_flags(d_backing_inode(dentry), 0); > > result = 0; > > } > > return result; > > } > > + > > +void ima_inode_post_removexattr(struct dentry *dentry, const char > *xattr_name) > > +{ > > + int result; > > + > > + result = ima_protect_xattr(dentry, xattr_name, NULL, 0); > > + if (result == 1) > > + ima_reset_appraise_flags(d_backing_inode(dentry), 0); > > +} > > Now you're calling ima_protect_xattr() twice for each removexattr. > Is that safe? Is it performant? Does it matter? > > > diff --git a/security/security.c b/security/security.c > > index 5ac96b16f8fa..efb1f874dc41 100644 > > --- a/security/security.c > > +++ b/security/security.c > > @@ -1319,6 +1319,7 @@ void security_inode_post_setxattr(struct dentry > *dentry, const char *name, > > if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) > > return; > > call_void_hook(inode_post_setxattr, dentry, name, value, size, > flags); > > + ima_inode_post_setxattr(dentry, name, value, size); > > evm_inode_post_setxattr(dentry, name, value, size); > > } > >
