diff options
Diffstat (limited to 'debian/patches/fix-refcount-assertion0002-ext2fs-fix-pager-use-after-free.patch')
| -rw-r--r-- | debian/patches/fix-refcount-assertion0002-ext2fs-fix-pager-use-after-free.patch | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/debian/patches/fix-refcount-assertion0002-ext2fs-fix-pager-use-after-free.patch b/debian/patches/fix-refcount-assertion0002-ext2fs-fix-pager-use-after-free.patch new file mode 100644 index 00000000..8809a309 --- /dev/null +++ b/debian/patches/fix-refcount-assertion0002-ext2fs-fix-pager-use-after-free.patch @@ -0,0 +1,87 @@ +From 60d14f5b3c4ea27af6f4220a15947c328bc888ee Mon Sep 17 00:00:00 2001 +From: Justus Winter <justus@gnupg.org> +Date: Sun, 22 May 2016 00:52:29 +0200 +Subject: [PATCH hurd 2/2] ext2fs: fix pager use-after-free + +Previously, pagers had no reference for being part of a node, only for +having a send right made for them. Hence we sometimes saw +use-after-free errors if the kernel did give up that send right, +typically while deleting files. Keep a weak reference as long as the +pager is referenced by a node. + +* ext2fs/pager.c (pager_clear_user_data): Assert that 'pager' has been +NULLed. +(pager_dropweak): Drop the weak reference and NULL 'pager'. +(diskfs_get_filemap): Simplify. Acquire a weak reference. +--- + ext2fs/pager.c | 31 ++++++++++++++++++++----------- + 1 file changed, 20 insertions(+), 11 deletions(-) + +diff --git a/ext2fs/pager.c b/ext2fs/pager.c +index 7d3a8f3..485f69c 100644 +--- a/ext2fs/pager.c ++++ b/ext2fs/pager.c +@@ -817,8 +817,7 @@ pager_clear_user_data (struct user_pager_info *upi) + + pthread_spin_lock (&node_to_page_lock); + pager = diskfs_node_disknode (upi->node)->pager; +- if (pager && pager_get_upi (pager) == upi) +- diskfs_node_disknode (upi->node)->pager = 0; ++ assert (!pager || pager_get_upi (pager) != upi); + pthread_spin_unlock (&node_to_page_lock); + + diskfs_nrele_light (upi->node); +@@ -831,8 +830,21 @@ pager_clear_user_data (struct user_pager_info *upi) + The pager library creates no weak references itself. If the user doesn't + either, then it's OK for this function to do nothing. */ + void +-pager_dropweak (struct user_pager_info *p __attribute__ ((unused))) ++pager_dropweak (struct user_pager_info *upi) + { ++ if (upi->type == FILE_DATA) ++ { ++ struct pager *pager; ++ ++ pthread_spin_lock (&node_to_page_lock); ++ pager = diskfs_node_disknode (upi->node)->pager; ++ if (pager && pager_get_upi (pager) == upi) ++ { ++ diskfs_node_disknode (upi->node)->pager = NULL; ++ ports_port_deref_weak (pager); ++ } ++ pthread_spin_unlock (&node_to_page_lock); ++ } + } + + /* Cached blocks from disk. */ +@@ -1298,15 +1310,9 @@ diskfs_get_filemap (struct node *node, vm_prot_t prot) + struct pager *pager = diskfs_node_disknode (node)->pager; + if (pager) + { +- /* Because PAGER is not a real reference, +- this might be nearly deallocated. If that's so, then +- the port right will be null. In that case, clear here +- and loop. The deallocation will complete separately. */ + right = pager_get_port (pager); +- if (right == MACH_PORT_NULL) +- diskfs_node_disknode (node)->pager = 0; +- else +- pager_get_upi (pager)->max_prot |= prot; ++ assert (MACH_PORT_VALID (right)); ++ pager_get_upi (pager)->max_prot |= prot; + } + else + { +@@ -1327,6 +1333,9 @@ diskfs_get_filemap (struct node *node, vm_prot_t prot) + return MACH_PORT_NULL; + } + ++ /* A weak reference for being part of the node. */ ++ ports_port_ref_weak (diskfs_node_disknode (node)->pager); ++ + right = pager_get_port (diskfs_node_disknode (node)->pager); + ports_port_deref (diskfs_node_disknode (node)->pager); + } +-- +2.1.4 + |