In the Linux kernel, the following vulnerability has been resolved:

gfs2: prevent NULL pointer dereference during unmount

When flushing out outstanding glock work during an unmount, gfs2logflush() can be called when sdp->sdjdesc has already been deallocated and sdp->sdjdesc is NULL. Commit 35264909e9d1 ("gfs2: Fix NULL pointer dereference in gfs2logflush") added a check for that to gfs2logflush() itself, but it missed the sdp->sdjdesc dereference in gfs2logrelease(). Fix that.

In the Linux kernel, the following vulnerability has been resolved:

gfs2: Fix use-after-free in iomap inline data write path

The inline data buffer head (dibh) is being released prematurely in gfs2iomapbegin() via releasemetapath() while iomap->inlinedata still points to dibh->bdata. This causes a use-after-free when iomapwriteendinline() later attempts to write to the inline data area.

The bug sequence: 1. gfs2iomapbegin() calls gfs2metainodebuffer() to read inode metadata into dibh 2. Sets iomap->inlinedata = dibh->bdata + sizeof(struct gfs2dinode) 3. Calls releasemetapath() which calls brelse(dibh), dropping refcount to 0 4. kswapd reclaims the page (~39ms later in the syzbot report) 5. iomapwriteendinline() tries to memcpy() to iomap->inlinedata 6. KASAN detects use-after-free write to freed memory

Fix by storing dibh in iomap->private and incrementing its refcount with getbh() in gfs2iomapbegin(). The buffer is then properly released in gfs2iomapend() after the inline write completes, ensuring the page stays alive for the entire iomap operation.

Note: A C reproducer is not available for this issue. The fix is based on analysis of the KASAN report and code review showing the buffer head is freed before use.

[agruenba: Take buffer head reference in gfs2iomapbegin() to avoid leaks in gfs2iomapget() and gfs2iomapalloc().]

In the Linux kernel, the following vulnerability has been resolved:

gfs2: fiemap page fault fix

In gfs2fiemap(), we are calling iomapfiemap() while holding the inode glock. This can lead to recursive glock taking if the fiemap buffer is memory mapped to the same inode and accessing it triggers a page fault.

Fix by disabling page faults for iomapfiemap() and faulting in the buffer by hand if necessary.

Fixes xfstest generic/742.

gfs2: Fix kernel NULL pointer dereference in gfs2rgrpdump

Syzkaller has reported a NULL pointer dereference when accessing rgd->rdrgl in gfs2rgrpdump(). This can happen when creatingrgd->rdgl fails in readrindexentry(). Add a NULL pointer check in gfs2rgrpdump() to prevent that.