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[Qemu-devel] [PATCH] linux-user: fix cmsg conversion in case of multiple
From: |
Jonathan Neuschäfer |
Subject: |
[Qemu-devel] [PATCH] linux-user: fix cmsg conversion in case of multiple headers |
Date: |
Thu, 3 Sep 2015 07:27:26 +0200 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
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.
Signed-off-by: Jonathan Neuschäfer <address@hidden>
--
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
Re: [Qemu-devel] [PATCH] linux-user: fix cmsg conversion in case of multiple headers, Riku Voipio, 2015/09/29