From e64e27d5cb103b7764f1a05b6eda7e7fedd517c5 Mon Sep 17 00:00:00 2001 From: Vitaly Chikunov Date: Wed, 16 Feb 2022 21:18:21 +0300 Subject: 9pfs: Fix segfault in do_readdir_many caused by struct dirent overread `struct dirent' returned from readdir(3) could be shorter (or longer) than `sizeof(struct dirent)', thus memcpy of sizeof length will overread into unallocated page causing SIGSEGV. Example stack trace: #0 0x00005555559ebeed v9fs_co_readdir_many (/usr/bin/qemu-system-x86_64 + 0x497eed) #1 0x00005555559ec2e9 v9fs_readdir (/usr/bin/qemu-system-x86_64 + 0x4982e9) #2 0x0000555555eb7983 coroutine_trampoline (/usr/bin/qemu-system-x86_64 + 0x963983) #3 0x00007ffff73e0be0 n/a (n/a + 0x0) While fixing this, provide a helper for any future `struct dirent' cloning. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/841 Cc: qemu-stable@nongnu.org Co-authored-by: Christian Schoenebeck Reviewed-by: Dmitry V. Levin Signed-off-by: Vitaly Chikunov Tested-by: Christian Schoenebeck Reviewed-by: Christian Schoenebeck Acked-by: Greg Kurz Tested-by: Vitaly Chikunov Message-Id: <20220216181821.3481527-1-vt@altlinux.org> [C.S. - Fix typo in source comment. ] Signed-off-by: Christian Schoenebeck --- hw/9pfs/9p-synth.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'hw/9pfs/9p-synth.h') diff --git a/hw/9pfs/9p-synth.h b/hw/9pfs/9p-synth.h index 036d7e4a5b..eeb246f377 100644 --- a/hw/9pfs/9p-synth.h +++ b/hw/9pfs/9p-synth.h @@ -41,6 +41,11 @@ typedef struct V9fsSynthOpenState { off_t offset; V9fsSynthNode *node; struct dirent dent; + /* + * Ensure there is enough space for 'dent' above, some systems have a + * d_name size of just 1, which would cause a buffer overrun. + */ + char dent_trailing_space[NAME_MAX]; } V9fsSynthOpenState; int qemu_v9fs_synth_mkdir(V9fsSynthNode *parent, int mode, -- cgit v1.2.3