From: Gao Xiang <hsiangkao@aol.com> To: linux-erofs@lists.ozlabs.org Cc: Chao Yu <yuchao0@huawei.com>, LKML <linux-kernel@vger.kernel.org>, Gao Xiang <hsiangkao@redhat.com>, stable@vger.kernel.org, Huang Jianan <huangjianan@oppo.com> Subject: [PATCH] erofs: initialized fields can only be observed after bit is set Date: Tue, 9 Feb 2021 21:06:18 +0800 [thread overview] Message-ID: <20210209130618.15838-1-hsiangkao@aol.com> (raw) In-Reply-To: 20210209130618.15838-1-hsiangkao.ref@aol.com From: Gao Xiang <hsiangkao@redhat.com> Currently, although set_bit() & test_bit() pairs are used as a fast- path for initialized configurations. However, these atomic ops are actually relaxed forms. Instead, load-acquire & store-release form is needed to make sure uninitialized fields won't be observed in advance here (yet no such corresponding bitops so use full barriers instead.) Fixes: 62dc45979f3f ("staging: erofs: fix race of initializing xattrs of a inode at the same time") Fixes: 152a333a5895 ("staging: erofs: add compacted compression indexes support") Cc: <stable@vger.kernel.org> # 5.3+ Reported-by: Huang Jianan <huangjianan@oppo.com> Signed-off-by: Gao Xiang <hsiangkao@redhat.com> --- fs/erofs/xattr.c | 10 +++++++++- fs/erofs/zmap.c | 10 +++++++++- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c index 5bde77d70852..47314a26767a 100644 --- a/fs/erofs/xattr.c +++ b/fs/erofs/xattr.c @@ -48,8 +48,14 @@ static int init_inode_xattrs(struct inode *inode) int ret = 0; /* the most case is that xattrs of this inode are initialized. */ - if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags)) + if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags)) { + /* + * paired with smp_mb() at the end of the function to ensure + * fields will only be observed after the bit is set. + */ + smp_mb(); return 0; + } if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_XATTR_BIT, TASK_KILLABLE)) return -ERESTARTSYS; @@ -137,6 +143,8 @@ static int init_inode_xattrs(struct inode *inode) } xattr_iter_end(&it, atomic_map); + /* paired with smp_mb() at the beginning of the function. */ + smp_mb(); set_bit(EROFS_I_EA_INITED_BIT, &vi->flags); out_unlock: diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index ae325541884e..14d2de35110c 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -36,8 +36,14 @@ static int z_erofs_fill_inode_lazy(struct inode *inode) void *kaddr; struct z_erofs_map_header *h; - if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags)) + if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags)) { + /* + * paired with smp_mb() at the end of the function to ensure + * fields will only be observed after the bit is set. + */ + smp_mb(); return 0; + } if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_Z_BIT, TASK_KILLABLE)) return -ERESTARTSYS; @@ -83,6 +89,8 @@ static int z_erofs_fill_inode_lazy(struct inode *inode) vi->z_physical_clusterbits[1] = vi->z_logical_clusterbits + ((h->h_clusterbits >> 5) & 7); + /* paired with smp_mb() at the beginning of the function */ + smp_mb(); set_bit(EROFS_I_Z_INITED_BIT, &vi->flags); unmap_done: kunmap_atomic(kaddr); -- 2.24.0
WARNING: multiple messages have this Message-ID (diff)
From: Gao Xiang via Linux-erofs <linux-erofs@lists.ozlabs.org> To: linux-erofs@lists.ozlabs.org Cc: LKML <linux-kernel@vger.kernel.org>, stable@vger.kernel.org Subject: [PATCH] erofs: initialized fields can only be observed after bit is set Date: Tue, 9 Feb 2021 21:06:18 +0800 [thread overview] Message-ID: <20210209130618.15838-1-hsiangkao@aol.com> (raw) In-Reply-To: 20210209130618.15838-1-hsiangkao.ref@aol.com From: Gao Xiang <hsiangkao@redhat.com> Currently, although set_bit() & test_bit() pairs are used as a fast- path for initialized configurations. However, these atomic ops are actually relaxed forms. Instead, load-acquire & store-release form is needed to make sure uninitialized fields won't be observed in advance here (yet no such corresponding bitops so use full barriers instead.) Fixes: 62dc45979f3f ("staging: erofs: fix race of initializing xattrs of a inode at the same time") Fixes: 152a333a5895 ("staging: erofs: add compacted compression indexes support") Cc: <stable@vger.kernel.org> # 5.3+ Reported-by: Huang Jianan <huangjianan@oppo.com> Signed-off-by: Gao Xiang <hsiangkao@redhat.com> --- fs/erofs/xattr.c | 10 +++++++++- fs/erofs/zmap.c | 10 +++++++++- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c index 5bde77d70852..47314a26767a 100644 --- a/fs/erofs/xattr.c +++ b/fs/erofs/xattr.c @@ -48,8 +48,14 @@ static int init_inode_xattrs(struct inode *inode) int ret = 0; /* the most case is that xattrs of this inode are initialized. */ - if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags)) + if (test_bit(EROFS_I_EA_INITED_BIT, &vi->flags)) { + /* + * paired with smp_mb() at the end of the function to ensure + * fields will only be observed after the bit is set. + */ + smp_mb(); return 0; + } if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_XATTR_BIT, TASK_KILLABLE)) return -ERESTARTSYS; @@ -137,6 +143,8 @@ static int init_inode_xattrs(struct inode *inode) } xattr_iter_end(&it, atomic_map); + /* paired with smp_mb() at the beginning of the function. */ + smp_mb(); set_bit(EROFS_I_EA_INITED_BIT, &vi->flags); out_unlock: diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index ae325541884e..14d2de35110c 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -36,8 +36,14 @@ static int z_erofs_fill_inode_lazy(struct inode *inode) void *kaddr; struct z_erofs_map_header *h; - if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags)) + if (test_bit(EROFS_I_Z_INITED_BIT, &vi->flags)) { + /* + * paired with smp_mb() at the end of the function to ensure + * fields will only be observed after the bit is set. + */ + smp_mb(); return 0; + } if (wait_on_bit_lock(&vi->flags, EROFS_I_BL_Z_BIT, TASK_KILLABLE)) return -ERESTARTSYS; @@ -83,6 +89,8 @@ static int z_erofs_fill_inode_lazy(struct inode *inode) vi->z_physical_clusterbits[1] = vi->z_logical_clusterbits + ((h->h_clusterbits >> 5) & 7); + /* paired with smp_mb() at the beginning of the function */ + smp_mb(); set_bit(EROFS_I_Z_INITED_BIT, &vi->flags); unmap_done: kunmap_atomic(kaddr); -- 2.24.0
next parent reply other threads:[~2021-02-09 13:08 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <20210209130618.15838-1-hsiangkao.ref@aol.com> 2021-02-09 13:06 ` Gao Xiang [this message] 2021-02-09 13:06 ` [PATCH] erofs: initialized fields can only be observed after bit is set Gao Xiang via Linux-erofs 2021-02-10 12:09 ` Chao Yu 2021-02-10 12:38 ` Gao Xiang 2021-02-10 12:38 ` Gao Xiang 2021-02-11 3:45 ` Chao Yu
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