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author | Bob Peterson <rpeterso@redhat.com> | 2016-06-09 14:24:07 -0500 |
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committer | Bob Peterson <rpeterso@redhat.com> | 2016-06-10 07:01:58 -0500 |
commit | 36e4ad0316c017d5b271378ed9a1c9a4b77fab5f (patch) | |
tree | 4a23a5f7ef511ce6b366c98cc0605bcb91985cb6 | |
parent | 29567292c0b5b2fb484125c280a2175141fe2205 (diff) | |
download | op-kernel-dev-36e4ad0316c017d5b271378ed9a1c9a4b77fab5f.zip op-kernel-dev-36e4ad0316c017d5b271378ed9a1c9a4b77fab5f.tar.gz |
GFS2: don't set rgrp gl_object until it's inserted into rgrp tree
Before this patch, function read_rindex_entry would set a rgrp
glock's gl_object pointer to itself before inserting the rgrp into
the rgrp rbtree. The problem is: if another process was also reading
the rgrp in, and had already inserted its newly created rgrp, then
the second call to read_rindex_entry would overwrite that value,
then return a bad return code to the caller. Later, other functions
would reference the now-freed rgrp memory by way of gl_object.
In some cases, that could result in gfs2_rgrp_brelse being called
twice for the same rgrp: once for the failed attempt and once for
the "real" rgrp release. Eventually the kernel would panic.
There are also a number of other things that could go wrong when
a kernel module is accessing freed storage. For example, this could
result in rgrp corruption because the fake rgrp would point to a
fake bitmap in memory too, causing gfs2_inplace_reserve to search
some random memory for free blocks, and find some, since we were
never setting rgd->rd_bits to NULL before freeing it.
This patch fixes the problem by not setting gl_object until we
have successfully inserted the rgrp into the rbtree. Also, it sets
rd_bits to NULL as it frees them, which will ensure any accidental
access to the wrong rgrp will result in a kernel panic rather than
file system corruption, which is preferred.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
-rw-r--r-- | fs/gfs2/rgrp.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c index 5bd2169..960aaf4 100644 --- a/fs/gfs2/rgrp.c +++ b/fs/gfs2/rgrp.c @@ -722,6 +722,7 @@ void gfs2_clear_rgrpd(struct gfs2_sbd *sdp) gfs2_free_clones(rgd); kfree(rgd->rd_bits); + rgd->rd_bits = NULL; return_all_reservations(rgd); kmem_cache_free(gfs2_rgrpd_cachep, rgd); } @@ -916,9 +917,6 @@ static int read_rindex_entry(struct gfs2_inode *ip) if (error) goto fail; - rgd->rd_gl->gl_object = rgd; - rgd->rd_gl->gl_vm.start = (rgd->rd_addr * bsize) & PAGE_MASK; - rgd->rd_gl->gl_vm.end = PAGE_ALIGN((rgd->rd_addr + rgd->rd_length) * bsize) - 1; rgd->rd_rgl = (struct gfs2_rgrp_lvb *)rgd->rd_gl->gl_lksb.sb_lvbptr; rgd->rd_flags &= ~(GFS2_RDF_UPTODATE | GFS2_RDF_PREFERRED); if (rgd->rd_data > sdp->sd_max_rg_data) @@ -926,14 +924,20 @@ static int read_rindex_entry(struct gfs2_inode *ip) spin_lock(&sdp->sd_rindex_spin); error = rgd_insert(rgd); spin_unlock(&sdp->sd_rindex_spin); - if (!error) + if (!error) { + rgd->rd_gl->gl_object = rgd; + rgd->rd_gl->gl_vm.start = (rgd->rd_addr * bsize) & PAGE_MASK; + rgd->rd_gl->gl_vm.end = PAGE_ALIGN((rgd->rd_addr + + rgd->rd_length) * bsize) - 1; return 0; + } error = 0; /* someone else read in the rgrp; free it and ignore it */ gfs2_glock_put(rgd->rd_gl); fail: kfree(rgd->rd_bits); + rgd->rd_bits = NULL; kmem_cache_free(gfs2_rgrpd_cachep, rgd); return error; } |