From 99fa8cb3c580d4445fe8fc239454e8f37a3b6847 Mon Sep 17 00:00:00 2001 From: David Chinner Date: Thu, 30 Oct 2008 17:36:40 +1100 Subject: [PATCH] [XFS] Prevent use-after-free caused by synchronous inode reclaim With the combined linux and XFS inode, we need to ensure that the combined structure is not freed before the generic code is finished with the inode. As it turns out, there is a case where the XFS inode is freed before the linux inode - when xfs_reclaim() is called from ->clear_inode() on a clean inode, the xfs inode is freed during that call. The generic code references the inode after the ->clear_inode() call, so this is a use after free situation. Fix the problem by moving the xfs_reclaim() call to ->destroy_inode() instead of in ->clear_inode(). This ensures the combined inode structure is not freed until after the generic code has finished with it. SGI-PV: 988141 SGI-Modid: xfs-linux-melb:xfs-kern:32324a Signed-off-by: David Chinner Signed-off-by: Lachlan McIlroy Signed-off-by: Christoph Hellwig --- fs/xfs/linux-2.6/xfs_super.c | 32 ++++++++++++++------------------ 1 file changed, 14 insertions(+), 18 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c index c6ef684bf2e..bb535a7737b 100644 --- a/fs/xfs/linux-2.6/xfs_super.c +++ b/fs/xfs/linux-2.6/xfs_super.c @@ -875,13 +875,18 @@ xfs_fs_alloc_inode( } /* - * we need to provide an empty inode free function to prevent - * the generic code from trying to free our combined inode. + * Now that the generic code is guaranteed not to be accessing + * the linux inode, we can reclaim the inode. */ STATIC void xfs_fs_destroy_inode( struct inode *inode) { + xfs_inode_t *ip = XFS_I(inode); + + XFS_STATS_INC(vn_reclaim); + if (xfs_reclaim(ip)) + panic("%s: cannot reclaim 0x%p\n", __func__, inode); } /* @@ -958,22 +963,13 @@ xfs_fs_clear_inode( { xfs_inode_t *ip = XFS_I(inode); - /* - * ip can be null when xfs_iget_core calls xfs_idestroy if we - * find an inode with di_mode == 0 but without IGET_CREATE set. - */ - if (ip) { - xfs_itrace_entry(ip); - XFS_STATS_INC(vn_rele); - XFS_STATS_INC(vn_remove); - XFS_STATS_INC(vn_reclaim); - XFS_STATS_DEC(vn_active); - - xfs_inactive(ip); - xfs_iflags_clear(ip, XFS_IMODIFIED); - if (xfs_reclaim(ip)) - panic("%s: cannot reclaim 0x%p\n", __func__, inode); - } + xfs_itrace_entry(ip); + XFS_STATS_INC(vn_rele); + XFS_STATS_INC(vn_remove); + XFS_STATS_DEC(vn_active); + + xfs_inactive(ip); + xfs_iflags_clear(ip, XFS_IMODIFIED); } STATIC void -- 2.11.4.GIT