Patchwork Fix page_check_range() wrap-around check when len=0.

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Submitter takasi-y@ops.dti.ne.jp
Date March 28, 2010, 12:53 a.m.
Message ID <201003280053.o2S0rrvk014831@smtp12.dti.ne.jp>
Download mbox | patch
Permalink /patch/48766/
State New
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takasi-y@ops.dti.ne.jp - March 28, 2010, 12:53 a.m.
Fix page_check_range() wrap-around check when len=0.

write(1,"",0) on linux-user emulation should be OK, but fails.
This is a regression brought by 376a7909.

This patch fixes it at the last of the calling path shown below,
  do_syscall:write -> access_ok() -> page_check_range(),
as linux-kernel does. For example, x86 does it at follows,
  sys_write() -> access_ok() -> __range_not_ok().
This implies calling page_check_range() with len=0 is valid.

Signed-off-by: Takashi YOSHII <takasi-y@ops.dti.ne.jp>
---
 exec.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

Patch

diff --git a/exec.c b/exec.c
index 14767b7..26cd8b9 100644
--- a/exec.c
+++ b/exec.c
@@ -2410,7 +2410,7 @@  int page_check_range(target_ulong start, target_ulong len, int flags)
     assert(start < ((abi_ulong)1 << L1_MAP_ADDR_SPACE_BITS));
 #endif
 
-    if (start + len - 1 < start) {
+    if (len > 0 && start + len -1 < start) {
         /* We've wrapped around.  */
         return -1;
     }