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authorBob Peterson <rpeterso@redhat.com>2016-06-09 22:24:07 +0300
committerBob Peterson <rpeterso@redhat.com>2016-06-10 15:01:58 +0300
commit36e4ad0316c017d5b271378ed9a1c9a4b77fab5f (patch)
tree4a23a5f7ef511ce6b366c98cc0605bcb91985cb6 /fs/gfs2
parent29567292c0b5b2fb484125c280a2175141fe2205 (diff)
downloadlinux-36e4ad0316c017d5b271378ed9a1c9a4b77fab5f.tar.xz
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>
Diffstat (limited to 'fs/gfs2')
-rw-r--r--fs/gfs2/rgrp.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 5bd216901e89..960aaf43d665 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;
}