07.02.2018 14:51, Dmitry Monakhov пишет: > Stanislav Kinsburskiy <skinsbur...@virtuozzo.com> writes: > >> Posix acl is used to convert of an extended attribute, provided by user to >> ext4 attributes. In particular to I-mode in case of ACL_TYPE_ACCESS request. >> IOW, this object is allocated, used for convertion, not stored anywhere and >> must be freed. >> However posix_acl_update_mode() can zerofy the pointer to support >> ext4_set_acl() logic, but then the object is leaked. >> So, fix it by releasing new temporary pointer with the same value instead of >> acl pointer. > So you are telling me that: > ext4_xattr_set_acl > L1 acl = posix_acl_from_xattr > L2 -> ext4_set_acl(handle, inode, type, acl) > L3 ->posix_acl_update_mode(inode, &inode->i_mode, &acl) > *acl = NULL; > You are saying that instruction above can affect value at L1? > HOW? acl passed to ext4_set_acl() by value, so > posix_acl_update_mode() can affect value only in L2 and L3 but not L1. > > Stas, have you drunk a lousy beer today?
OMG, Dmitry... Looks like storage work clouded your mind and you are looking to some other sources. There is no "L3" in the bug. Because posix_acl_update_mode() in called from ext4_xattr_set_acl() (i.e on "L2"). Thus pointer is set to NULL on "L2" and released on "L1". IOW, pointer is leaked. >> >> https://jira.sw.ru/browse/PSBM-81384 >> >> Signed-off-by: Stanislav Kinsburskiy <skinsbur...@virtuozzo.com> >> --- >> fs/ext4/acl.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c >> index 917e819..2640d7b 100644 >> --- a/fs/ext4/acl.c >> +++ b/fs/ext4/acl.c >> @@ -403,7 +403,7 @@ ext4_xattr_set_acl(struct dentry *dentry, const char >> *name, const void *value, >> { >> struct inode *inode = dentry->d_inode; >> handle_t *handle; >> - struct posix_acl *acl; >> + struct posix_acl *acl, *tmp; >> int error, retries = 0; >> int update_mode = 0; >> umode_t mode = inode->i_mode; >> @@ -416,7 +416,7 @@ ext4_xattr_set_acl(struct dentry *dentry, const char >> *name, const void *value, >> return -EPERM; >> >> if (value) { >> - acl = posix_acl_from_xattr(&init_user_ns, value, size); >> + acl = tmp = posix_acl_from_xattr(&init_user_ns, value, size); >> if (IS_ERR(acl)) >> return PTR_ERR(acl); >> else if (acl) { >> @@ -425,7 +425,7 @@ ext4_xattr_set_acl(struct dentry *dentry, const char >> *name, const void *value, >> goto release_and_out; >> } >> } else >> - acl = NULL; >> + acl = tmp = NULL; >> >> retry: >> handle = ext4_journal_start(inode, EXT4_HT_XATTR, >> @@ -452,7 +452,7 @@ ext4_xattr_set_acl(struct dentry *dentry, const char >> *name, const void *value, >> goto retry; >> >> release_and_out: >> - posix_acl_release(acl); >> + posix_acl_release(tmp); >> return error; >> } >> _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
