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 --- include/qemu/osdep.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/qemu') diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index d1660d6..ce12f64 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -805,6 +805,19 @@ static inline int platform_does_not_support_system(const char *command) } #endif /* !HAVE_SYSTEM_FUNCTION */ +/** + * Duplicate directory entry @dent. + * + * It is highly recommended to use this function instead of open coding + * duplication of @c dirent objects, because the actual @c struct @c dirent + * size may be bigger or shorter than @c sizeof(struct dirent) and correct + * handling is platform specific (see gitlab issue #841). + * + * @dent - original directory entry to be duplicated + * @returns duplicated directory entry which should be freed with g_free() + */ +struct dirent *qemu_dirent_dup(struct dirent *dent); + #ifdef __cplusplus } #endif -- cgit v1.1