[libvirt] [PATCH] buf: Fix possible infinite loop in EscapeString, VSnprintf
The current code will go into an infinite loop if the printf generated
string is >= 1000, AND exactly 1 character smaller than the amount of free
space in the buffer. When this happens, we are dropped into the loop body,
but nothing will actually change, because count == (buf->size - buf->use - 1),
and virBufferGrow returns unchanged if count < (buf->size - buf->use)
Fix this by removing the '- 1' bit from 'size'. The *nprintf functions
handle
the NULL byte for us anyways, so we shouldn't need to manually accomodate
for it.
Here's a bug where we are actually hitting this issue:
https://bugzilla.redhat.com/show_bug.cgi?id=602772
Signed-off-by: Cole Robinson <crobinso(a)redhat.com>
---
src/util/buf.c | 14 ++++++--------
1 files changed, 6 insertions(+), 8 deletions(-)
diff --git a/src/util/buf.c b/src/util/buf.c
index fc1217b..734b8f6 100644
--- a/src/util/buf.c
+++ b/src/util/buf.c
@@ -236,11 +236,11 @@ virBufferVSprintf(const virBufferPtr buf, const char *format, ...)
virBufferGrow(buf, 100) < 0)
return;
- size = buf->size - buf->use - 1;
+ size = buf->size - buf->use;
va_start(argptr, format);
va_copy(locarg, argptr);
while (((count = vsnprintf(&buf->content[buf->use], size, format,
- locarg)) < 0) || (count >= size - 1)) {
+ locarg)) < 0) || (count >= size)) {
buf->content[buf->use] = 0;
va_end(locarg);
@@ -250,13 +250,12 @@ virBufferVSprintf(const virBufferPtr buf, const char *format, ...)
return;
}
- size = buf->size - buf->use - 1;
+ size = buf->size - buf->use;
va_copy(locarg, argptr);
}
va_end(argptr);
va_end(locarg);
buf->use += count;
- buf->content[buf->use] = '\0';
}
/**
@@ -340,19 +339,18 @@ virBufferEscapeString(const virBufferPtr buf, const char *format,
const char *st
return;
}
- size = buf->size - buf->use - 1;
+ size = buf->size - buf->use;
while (((count = snprintf(&buf->content[buf->use], size, format,
- (char *)escaped)) < 0) || (count >= size - 1)) {
+ (char *)escaped)) < 0) || (count >= size)) {
buf->content[buf->use] = 0;
grow_size = (count > 1000) ? count : 1000;
if (virBufferGrow(buf, grow_size) < 0) {
VIR_FREE(escaped);
return;
}
- size = buf->size - buf->use - 1;
+ size = buf->size - buf->use;
}
buf->use += count;
- buf->content[buf->use] = '\0';
VIR_FREE(escaped);
}
--
1.7.2.1