From: Dave Chinner <dchinner(a)redhat.com>
[ Upstream commit 118e021b4b66f758f8e8f21dc0e5e0a4c721e69e ]
When we reserve a delalloc region in xfs_buffered_write_iomap_begin,
we mark the iomap as IOMAP_F_NEW so that the the write context
understands that it allocated the delalloc region.
If we then fail that buffered write, xfs_buffered_write_iomap_end()
checks for the IOMAP_F_NEW flag and if it is set, it punches out
the unused delalloc region that was allocated for the write.
The assumption this code makes is that all buffered write operations
that can allocate space are run under an exclusive lock (i_rwsem).
This is an invalid assumption: page faults in mmap()d regions call
through this same function pair to map the file range being faulted
and this runs only holding the inode->i_mapping->invalidate_lock in
shared mode.
IOWs, we can have races between page faults and write() calls that
fail the nested page cache write operation that result in data loss.
That is, the failing iomap_end call will punch out the data that
the other racing iomap iteration brought into the page cache. This
can be reproduced with generic/34[46] if we arbitrarily fail page
cache copy-in operations from write() syscalls.
Code analysis tells us that the iomap_page_mkwrite() function holds
the already instantiated and uptodate folio locked across the iomap
mapping iterations. Hence the folio cannot be removed from memory
whilst we are mapping the range it covers, and as such we do not
care if the mapping changes state underneath the iomap iteration
loop:
1. if the folio is not already dirty, there is no writeback races
possible.
2. if we allocated the mapping (delalloc or unwritten), the folio
cannot already be dirty. See #1.
3. If the folio is already dirty, it must be up to date. As we hold
it locked, it cannot be reclaimed from memory. Hence we always
have valid data in the page cache while iterating the mapping.
4. Valid data in the page cache can exist when the underlying
mapping is DELALLOC, UNWRITTEN or WRITTEN. Having the mapping
change from DELALLOC->UNWRITTEN or UNWRITTEN->WRITTEN does not
change the data in the page - it only affects actions if we are
initialising a new page. Hence #3 applies and we don't care
about these extent map transitions racing with
iomap_page_mkwrite().
5. iomap_page_mkwrite() checks for page invalidation races
(truncate, hole punch, etc) after it locks the folio. We also
hold the mapping->invalidation_lock here, and hence the mapping
cannot change due to extent removal operations while we are
iterating the folio.
As such, filesystems that don't use bufferheads will never fail
the iomap_folio_mkwrite_iter() operation on the current mapping,
regardless of whether the iomap should be considered stale.
Further, the range we are asked to iterate is limited to the range
inside EOF that the folio spans. Hence, for XFS, we will only map
the exact range we are asked for, and we will only do speculative
preallocation with delalloc if we are mapping a hole at the EOF
page. The iterator will consume the entire range of the folio that
is within EOF, and anything beyond the EOF block cannot be accessed.
We never need to truncate this post-EOF speculative prealloc away in
the context of the iomap_page_mkwrite() iterator because if it
remains unused we'll remove it when the last reference to the inode
goes away.
Hence we don't actually need an .iomap_end() cleanup/error handling
path at all for iomap_page_mkwrite() for XFS. This means we can
separate the page fault processing from the complexity of the
.iomap_end() processing in the buffered write path. This also means
that the buffered write path will also be able to take the
mapping->invalidate_lock as necessary.
Signed-off-by: Dave Chinner <dchinner(a)redhat.com>
Reviewed-by: Christoph Hellwig <hch(a)lst.de>
Reviewed-by: Darrick J. Wong <djwong(a)kernel.org>
Signed-off-by: Leah Rumancik <leah.rumancik(a)gmail.com>
Acked-by: Darrick J. Wong <djwong(a)kernel.org>
---
fs/xfs/xfs_file.c | 2 +-
fs/xfs/xfs_iomap.c | 9 +++++++++
fs/xfs/xfs_iomap.h | 1 +
3 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index e462d39c840e..595a5bcf46b9 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1325,7 +1325,7 @@ __xfs_filemap_fault(
if (write_fault) {
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
ret = iomap_page_mkwrite(vmf,
- &xfs_buffered_write_iomap_ops);
+ &xfs_page_mkwrite_iomap_ops);
xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
} else {
ret = filemap_fault(vmf);
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 07da03976ec1..5cea069a38b4 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1187,6 +1187,15 @@ const struct iomap_ops xfs_buffered_write_iomap_ops = {
.iomap_end = xfs_buffered_write_iomap_end,
};
+/*
+ * iomap_page_mkwrite() will never fail in a way that requires delalloc extents
+ * that it allocated to be revoked. Hence we do not need an .iomap_end method
+ * for this operation.
+ */
+const struct iomap_ops xfs_page_mkwrite_iomap_ops = {
+ .iomap_begin = xfs_buffered_write_iomap_begin,
+};
+
static int
xfs_read_iomap_begin(
struct inode *inode,
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index c782e8c0479c..0f62ab633040 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -47,6 +47,7 @@ xfs_aligned_fsb_count(
}
extern const struct iomap_ops xfs_buffered_write_iomap_ops;
+extern const struct iomap_ops xfs_page_mkwrite_iomap_ops;
extern const struct iomap_ops xfs_direct_write_iomap_ops;
extern const struct iomap_ops xfs_read_iomap_ops;
extern const struct iomap_ops xfs_seek_iomap_ops;
--
2.45.0.rc1.225.g2a3ae87e7f-goog
On Thu, May 23, 2024 at 08:21:23AM +0000, Lin Gui (桂林) wrote:
> Dear @Greg KH<mailto:gregkh@linuxfoundation.org>,
>
>
> I don't understand, why does this qualify as a stable patch? The
>
> changes says this is "optional", which means the device should work just
>
> fine without it, right?
>
> [MTK]
>
> If without this patch, some emmc devices may cause unstable operation and report CRC errors.
>
>
>
> Is this a regression fix from something that previously used to work
>
> properly?
> [MTK]
> Yes
Ok, thanks. But you need to provide a working, and tested, version of
it for 5.15.y as it obviously does not even work there (which means you
did not test that?)
greg k-h
In the prueth_probe() function, if one of the calls to emac_phy_connect()
fails due to of_phy_connect() returning NULL, then the subsequent call to
phy_attached_info() will dereference a NULL pointer.
Check the return code of emac_phy_connect and fail cleanly if there is an
error.
Fixes: 128d5874c082 ("net: ti: icssg-prueth: Add ICSSG ethernet driver")
Cc: stable(a)vger.kernel.org
Signed-off-by: Romain Gantois <romain.gantois(a)bootlin.com>
---
Hello everyone,
There is a possible NULL pointer dereference in the prueth_probe() function of
the icssg_prueth driver. I discovered this while testing a platform with one
PRUETH MAC enabled out of the two available.
These are the requirements to reproduce the bug:
prueth_probe() is called
either eth0_node or eth1_node is not NULL
in emac_phy_connect: of_phy_connect() returns NULL
Then, the following leads to the NULL pointer dereference:
prueth->emac[PRUETH_MAC0]->ndev->phydev is set to NULL
prueth->emac[PRUETH_MAC0]->ndev->phydev is passed to phy_attached_info()
-> phy_attached_print() dereferences phydev which is NULL
This series provides a fix by checking the return code of emac_phy_connect().
Best Regards,
Romain
---
drivers/net/ethernet/ti/icssg/icssg_prueth.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth.c b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
index 7c9e9518f555a..1ea3fbd5e954e 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_prueth.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
@@ -1039,7 +1039,12 @@ static int prueth_probe(struct platform_device *pdev)
prueth->registered_netdevs[PRUETH_MAC0] = prueth->emac[PRUETH_MAC0]->ndev;
- emac_phy_connect(prueth->emac[PRUETH_MAC0]);
+ ret = emac_phy_connect(prueth->emac[PRUETH_MAC0]);
+ if (ret) {
+ dev_err(dev,
+ "can't connect to MII0 PHY, error -%d", ret);
+ goto netdev_unregister;
+ }
phy_attached_info(prueth->emac[PRUETH_MAC0]->ndev->phydev);
}
@@ -1051,7 +1056,12 @@ static int prueth_probe(struct platform_device *pdev)
}
prueth->registered_netdevs[PRUETH_MAC1] = prueth->emac[PRUETH_MAC1]->ndev;
- emac_phy_connect(prueth->emac[PRUETH_MAC1]);
+ ret = emac_phy_connect(prueth->emac[PRUETH_MAC1]);
+ if (ret) {
+ dev_err(dev,
+ "can't connect to MII1 PHY, error %d", ret);
+ goto netdev_unregister;
+ }
phy_attached_info(prueth->emac[PRUETH_MAC1]->ndev->phydev);
}
---
base-commit: e4a87abf588536d1cdfb128595e6e680af5cf3ed
change-id: 20240521-icssg-prueth-fix-03b03064c5ce
Best regards,
--
Romain Gantois <romain.gantois(a)bootlin.com>