This is a note to let you know that I've just added the patch titled
erofs: initialized fields can only be observed after bit is set
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
erofs-initialized-fields-can-only-be-observed-after-bit-is-set.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ce063129181312f8781a047a50be439c5859747b Mon Sep 17 00:00:00 2001
From: Gao Xiang <hsiangkao@xxxxxxxxxx>
Date: Tue, 9 Feb 2021 21:06:18 +0800
Subject: erofs: initialized fields can only be observed after bit is set
From: Gao Xiang <hsiangkao@xxxxxxxxxx>
commit ce063129181312f8781a047a50be439c5859747b upstream.
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.)
Link: https://lore.kernel.org/r/20210209130618.15838-1-hsiangkao@xxxxxxx
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@xxxxxxxxxxxxxxx> # 5.3+
Reported-by: Huang Jianan <huangjianan@xxxxxxxx>
Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/erofs/xattr.c | 10 +++++++++-
fs/erofs/zmap.c | 10 +++++++++-
2 files changed, 18 insertions(+), 2 deletions(-)
--- a/fs/erofs/xattr.c
+++ b/fs/erofs/xattr.c
@@ -48,8 +48,14 @@ static int init_inode_xattrs(struct inod
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 inod
}
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:
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -36,8 +36,14 @@ static int z_erofs_fill_inode_lazy(struc
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(struc
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);
Patches currently in stable-queue which might be from hsiangkao@xxxxxxxxxx are
queue-5.11/erofs-initialized-fields-can-only-be-observed-after-bit-is-set.patch
