Hi,
On Thu, Sep 03, 2015 at 07:27:26AM +0200, Jonathan Neuschäfer wrote:
> Currently, __target_cmsg_nxthdr compares a pointer derived from
> target_cmsg against the msg_control field of target_msgh (through
> subtraction). This failed for me when emulating i386 code under x86_64,
> because pointers in the host address space and pointers in the guest
> address space were not the same. This patch passes the initial value of
> target_cmsg into __target_cmsg_nxthdr.
>
> I found and fixed two more related bugs:
> - __target_cmsg_nxthdr now returns the new cmsg pointer instead of the
> old one.
> - tgt_space (in host_to_target_cmsg) doesn't count "sizeof (struct
> target_cmsghdr)" twice anymore.
Applied to linux-user tree, thanks.
> Signed-off-by: Jonathan Neuschäfer <j.neuschae...@gmx.net>
> --
For next time, use three dashes "---" to separate version-to-version
change descriptions from commit messages. This way git will
automatically leave them out when doing git am.
> Changes since v2:
> - The patch is now clean WRT checkpatch.pl
> Changes since v1:
> - Follow Peter Maydell's advice on how to fix the first bug
> - The "two more related bugs"
> ---
> linux-user/syscall.c | 14 +++++++++-----
> linux-user/syscall_defs.h | 14 +++++++++-----
> 2 files changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index f62c698..12a6cd2 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -1181,7 +1181,7 @@ static inline abi_long target_to_host_cmsg(struct
> msghdr *msgh,
> struct cmsghdr *cmsg = CMSG_FIRSTHDR(msgh);
> abi_long msg_controllen;
> abi_ulong target_cmsg_addr;
> - struct target_cmsghdr *target_cmsg;
> + struct target_cmsghdr *target_cmsg, *target_cmsg_start;
> socklen_t space = 0;
>
> msg_controllen = tswapal(target_msgh->msg_controllen);
> @@ -1189,6 +1189,7 @@ static inline abi_long target_to_host_cmsg(struct
> msghdr *msgh,
> goto the_end;
> target_cmsg_addr = tswapal(target_msgh->msg_control);
> target_cmsg = lock_user(VERIFY_READ, target_cmsg_addr, msg_controllen,
> 1);
> + target_cmsg_start = target_cmsg;
> if (!target_cmsg)
> return -TARGET_EFAULT;
>
> @@ -1247,7 +1248,8 @@ static inline abi_long target_to_host_cmsg(struct
> msghdr *msgh,
> }
>
> cmsg = CMSG_NXTHDR(msgh, cmsg);
> - target_cmsg = TARGET_CMSG_NXTHDR(target_msgh, target_cmsg);
> + target_cmsg = TARGET_CMSG_NXTHDR(target_msgh, target_cmsg,
> + target_cmsg_start);
> }
> unlock_user(target_cmsg, target_cmsg_addr, 0);
> the_end:
> @@ -1261,7 +1263,7 @@ static inline abi_long host_to_target_cmsg(struct
> target_msghdr *target_msgh,
> struct cmsghdr *cmsg = CMSG_FIRSTHDR(msgh);
> abi_long msg_controllen;
> abi_ulong target_cmsg_addr;
> - struct target_cmsghdr *target_cmsg;
> + struct target_cmsghdr *target_cmsg, *target_cmsg_start;
> socklen_t space = 0;
>
> msg_controllen = tswapal(target_msgh->msg_controllen);
> @@ -1269,6 +1271,7 @@ static inline abi_long host_to_target_cmsg(struct
> target_msghdr *target_msgh,
> goto the_end;
> target_cmsg_addr = tswapal(target_msgh->msg_control);
> target_cmsg = lock_user(VERIFY_WRITE, target_cmsg_addr, msg_controllen,
> 0);
> + target_cmsg_start = target_cmsg;
> if (!target_cmsg)
> return -TARGET_EFAULT;
>
> @@ -1382,14 +1385,15 @@ static inline abi_long host_to_target_cmsg(struct
> target_msghdr *target_msgh,
> }
>
> target_cmsg->cmsg_len = tswapal(tgt_len);
> - tgt_space = TARGET_CMSG_SPACE(tgt_len);
> + tgt_space = TARGET_CMSG_SPACE(len);
> if (msg_controllen < tgt_space) {
> tgt_space = msg_controllen;
> }
> msg_controllen -= tgt_space;
> space += tgt_space;
> cmsg = CMSG_NXTHDR(msgh, cmsg);
> - target_cmsg = TARGET_CMSG_NXTHDR(target_msgh, target_cmsg);
> + target_cmsg = TARGET_CMSG_NXTHDR(target_msgh, target_cmsg,
> + target_cmsg_start);
> }
> unlock_user(target_cmsg, target_cmsg_addr, space);
> the_end:
> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> index edd5f3c..9d3c537 100644
> --- a/linux-user/syscall_defs.h
> +++ b/linux-user/syscall_defs.h
> @@ -234,7 +234,8 @@ struct target_cmsghdr {
> };
>
> #define TARGET_CMSG_DATA(cmsg) ((unsigned char *) ((struct target_cmsghdr *)
> (cmsg) + 1))
> -#define TARGET_CMSG_NXTHDR(mhdr, cmsg) __target_cmsg_nxthdr (mhdr, cmsg)
> +#define TARGET_CMSG_NXTHDR(mhdr, cmsg, cmsg_start) \
> + __target_cmsg_nxthdr(mhdr, cmsg, cmsg_start)
> #define TARGET_CMSG_ALIGN(len) (((len) + sizeof (abi_long) - 1) \
> & (size_t) ~(sizeof (abi_long) - 1))
> #define TARGET_CMSG_SPACE(len) (TARGET_CMSG_ALIGN (len) \
> @@ -242,17 +243,20 @@ struct target_cmsghdr {
> #define TARGET_CMSG_LEN(len) (TARGET_CMSG_ALIGN (sizeof (struct
> target_cmsghdr)) + (len))
>
> static __inline__ struct target_cmsghdr *
> -__target_cmsg_nxthdr (struct target_msghdr *__mhdr, struct target_cmsghdr
> *__cmsg)
> +__target_cmsg_nxthdr(struct target_msghdr *__mhdr,
> + struct target_cmsghdr *__cmsg,
> + struct target_cmsghdr *__cmsg_start)
> {
> struct target_cmsghdr *__ptr;
>
> __ptr = (struct target_cmsghdr *)((unsigned char *) __cmsg
> + TARGET_CMSG_ALIGN
> (tswapal(__cmsg->cmsg_len)));
> - if ((unsigned long)((char *)(__ptr+1) - (char
> *)(size_t)tswapal(__mhdr->msg_control))
> - > tswapal(__mhdr->msg_controllen))
> + if ((unsigned long)((char *)(__ptr+1) - (char *)__cmsg_start)
> + > tswapal(__mhdr->msg_controllen)) {
> /* No more entries. */
> return (struct target_cmsghdr *)0;
> - return __cmsg;
> + }
> + return __ptr;
> }
>
> struct target_mmsghdr {
> --
> 2.5.0
>
