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gfs2: Fix underflow in gfs2_page_mkwrite

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commit d3c51c55cb upstream.

On filesystems with a block size smaller than PAGE_SIZE and non-empty
files smaller then PAGE_SIZE, gfs2_page_mkwrite could end up allocating
excess blocks beyond the end of the file, similar to fallocate.  This
doesn't make sense; fix it.

Reported-by: Bob Peterson <rpeterso@redhat.com>
Fixes: 184b4e6085 ("gfs2: Fix end-of-file handling in gfs2_page_mkwrite")
Cc: stable@vger.kernel.org # v5.5+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Andreas Gruenbacher 2021-06-21 22:28:50 +02:00 • committed by Greg Kroah-Hartman
commit 3ae1c663bd
1 changed files with 2 additions and 2 deletions
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4
fs/gfs2/file.c
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@ -474,8 +474,8 @@ static vm_fault_t gfs2_page_mkwrite(struct vm_fault *vmf)
file_update_time(vmf->vma->vm_file);
/* page is wholly or partially inside EOF */
if (offset > size - PAGE_SIZE)
length = offset_in_page(size);
if (size - offset < PAGE_SIZE)
length = size - offset;
else
length = PAGE_SIZE;