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gfs2: fix glock reference problem in gfs2_trans_remove_revoke 

Commit 9287c6452d fixed a situation in which gfs2 could use a glock
after it had been freed. To do that, it temporarily added a new glock
reference by calling gfs2_glock_hold in function gfs2_add_revoke.
However, if the bd element was removed by gfs2_trans_remove_revoke, it
failed to drop the additional reference.

This patch adds logic to gfs2_trans_remove_revoke to properly drop the
additional glock reference.

Fixes: 9287c6452d ("gfs2: Fix occasional glock use-after-free")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Bob Peterson 2019-11-14 09:49:11 -05:00 committed by Andreas Gruenbacher
parent feed98a8e5
commit fe5e7ba11f
4 changed files with 12 additions and 4 deletions
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8
fs/gfs2/log.c
View File

@ -611,6 +611,14 @@ void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
list_add(&bd->bd_list, &sdp->sd_log_revokes);
}
void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
{
if (atomic_dec_return(&gl->gl_revokes) == 0) {
clear_bit(GLF_LFLUSH, &gl->gl_flags);
gfs2_glock_queue_put(gl);
}
}
void gfs2_write_revokes(struct gfs2_sbd *sdp)
{
struct gfs2_trans *tr;

1
fs/gfs2/log.h
View File

@ -76,6 +76,7 @@ extern void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
extern int gfs2_logd(void *data);
extern void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd);
extern void gfs2_glock_remove_revoke(struct gfs2_glock *gl);
extern void gfs2_write_revokes(struct gfs2_sbd *sdp);
#endif /* __LOG_DOT_H__ */

5
fs/gfs2/lops.c
View File

@ -883,10 +883,7 @@ static void revoke_lo_after_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
bd = list_entry(head->next, struct gfs2_bufdata, bd_list);
list_del_init(&bd->bd_list);
gl = bd->bd_gl;
if (atomic_dec_return(&gl->gl_revokes) == 0) {
clear_bit(GLF_LFLUSH, &gl->gl_flags);
gfs2_glock_queue_put(gl);
}
gfs2_glock_remove_revoke(gl);
kmem_cache_free(gfs2_bufdata_cachep, bd);
}
}

2
fs/gfs2/trans.c
View File

@ -262,6 +262,8 @@ void gfs2_trans_remove_revoke(struct gfs2_sbd *sdp, u64 blkno, unsigned int len)
list_del_init(&bd->bd_list);
gfs2_assert_withdraw(sdp, sdp->sd_log_num_revoke);
sdp->sd_log_num_revoke--;
if (bd->bd_gl)
gfs2_glock_remove_revoke(bd->bd_gl);
kmem_cache_free(gfs2_bufdata_cachep, bd);
tr->tr_num_revoke--;
if (--n == 0)