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* [glibc] syslog: Fix heap buffer overflow in __vsyslog_internal (CVE-2023-6779)
@ 2024-01-30 18:02 Arjun Shankar
0 siblings, 0 replies; only message in thread
From: Arjun Shankar @ 2024-01-30 18:02 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=7e5a0c286da33159d47d0122007aac016f3e02cd
commit 7e5a0c286da33159d47d0122007aac016f3e02cd
Author: Arjun Shankar <arjun@redhat.com>
Date: Mon Jan 15 17:44:44 2024 +0100
syslog: Fix heap buffer overflow in __vsyslog_internal (CVE-2023-6779)
__vsyslog_internal used the return value of snprintf/vsnprintf to
calculate buffer sizes for memory allocation. If these functions (for
any reason) failed and returned -1, the resulting buffer would be too
small to hold output. This commit fixes that.
All snprintf/vsnprintf calls are checked for negative return values and
the function silently returns upon encountering them.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Diff:
---
misc/syslog.c | 39 ++++++++++++++++++++++++++++-----------
1 file changed, 28 insertions(+), 11 deletions(-)
diff --git a/misc/syslog.c b/misc/syslog.c
index 814d224a1e..53440e47ad 100644
--- a/misc/syslog.c
+++ b/misc/syslog.c
@@ -185,11 +185,13 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
else
l = __snprintf (bufs, sizeof bufs,
SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+ if (l < 0)
+ goto out;
char *pos;
size_t len;
- if (0 <= l && l < sizeof bufs)
+ if (l < sizeof bufs)
{
/* At this point, there is still a chance that we can print the
remaining part of the log into bufs and use that. */
@@ -215,12 +217,15 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
__set_errno (saved_errno);
vl = __vsnprintf_internal (pos, len, fmt, apc, mode_flags);
+ va_end (apc);
+
+ if (vl < 0)
+ goto out;
- if (!(0 <= vl && vl < len))
+ if (vl >= len)
buf = NULL;
bufsize = l + vl;
- va_end (apc);
}
if (buf == NULL)
@@ -231,25 +236,37 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
/* Tell the cancellation handler to free this buffer. */
clarg.buf = buf;
+ int cl;
if (has_ts)
- __snprintf (buf, l + 1,
- SYSLOG_HEADER (pri, timestamp, &msgoff, pid));
+ cl = __snprintf (buf, l + 1,
+ SYSLOG_HEADER (pri, timestamp, &msgoff, pid));
else
- __snprintf (buf, l + 1,
- SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+ cl = __snprintf (buf, l + 1,
+ SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+ if (cl != l)
+ goto out;
va_list apc;
va_copy (apc, ap);
- __vsnprintf_internal (buf + l, bufsize - l + 1, fmt, apc,
- mode_flags);
+ cl = __vsnprintf_internal (buf + l, bufsize - l + 1, fmt, apc,
+ mode_flags);
va_end (apc);
+
+ if (cl != vl)
+ goto out;
}
else
{
+ int bl;
/* Nothing much to do but emit an error message. */
- bufsize = __snprintf (bufs, sizeof bufs,
- "out of memory[%d]", __getpid ());
+ bl = __snprintf (bufs, sizeof bufs,
+ "out of memory[%d]", __getpid ());
+ if (bl < 0 || bl >= sizeof bufs)
+ goto out;
+
+ bufsize = bl;
buf = bufs;
+ msgoff = 0;
}
}
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