83 lines
2.9 KiB
Diff
83 lines
2.9 KiB
Diff
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Subject: [PATCH] [BZ 184060] zipl/libc: Indicate truncated lines in printf with '...'
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From: Philipp Rudo <prudo@linux.ibm.com>
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Description: zipl/libc: Fix potential buffer overflow in printf
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Symptom: Crash of the zipl boot loader during boot.
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Problem: The zipl boot loaders have their own minimalistic libc
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implementation. In it printf and sprintf use vsprintf for string
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formatting. Per definition vsprintf assumes that the buffer it
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writes to is large enough to contain the formatted string and
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performs no size checks. This is problematic for the boot
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loaders because the buffer they use are often allocated on the
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stack. Thus even small changes to the string format can
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potentially cause buffer overflows on the stack.
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Solution: Implement vsnprintf and make use of it.
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Reproduction: Use printf to print a string with >81 characters (exact number
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depends on the stack layout/compiler used).
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Upstream-ID: 36fed0e6c6590631c4ce1707c8fe3c3397bcce4d
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Problem-ID: 184060
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Upstream-Description:
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zipl/libc: Indicate truncated lines in printf with '...'
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Append '...' to lines exceeding the maximum line length instead of
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silently truncating them.
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Suggested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
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Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
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Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
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Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
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Signed-off-by: Jan Hoeppner <hoeppner@linux.ibm.com>
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Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
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---
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zipl/boot/libc.c | 10 ++++++++--
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zipl/boot/libc.h | 1 +
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zipl/boot/menu.h | 1 -
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3 files changed, 9 insertions(+), 3 deletions(-)
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--- a/zipl/boot/libc.c
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+++ b/zipl/boot/libc.c
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@@ -408,11 +408,17 @@ void snprintf(char *buf, unsigned long s
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*/
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void printf(const char *fmt, ...)
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{
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- char buf[81];
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+ char buf[LINE_LENGTH + 1];
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+ int len;
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va_list va;
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va_start(va, fmt);
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- vsnprintf(buf, sizeof(buf), fmt, va);
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+ len = vsnprintf(buf, sizeof(buf), fmt, va);
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+ if (len > LINE_LENGTH) {
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+ buf[LINE_LENGTH - 1] = '.';
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+ buf[LINE_LENGTH - 2] = '.';
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+ buf[LINE_LENGTH - 3] = '.';
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+ }
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sclp_print(buf);
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va_end(va);
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}
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--- a/zipl/boot/libc.h
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+++ b/zipl/boot/libc.h
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@@ -40,6 +40,7 @@
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#define ENOTTY 25 /* Not a typewriter */
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#define MIB (1024ULL * 1024)
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+#define LINE_LENGTH 80 /* max line length printed by printf */
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typedef unsigned long long uint64_t;
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typedef unsigned int uint32_t;
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--- a/zipl/boot/menu.h
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+++ b/zipl/boot/menu.h
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@@ -20,7 +20,6 @@
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/* max command line length */
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#define COMMAND_LINE_SIZE 896
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#define BOOT_MENU_ENTRIES 63
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-#define LINE_LENGTH 80
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#define PARAM_SIZE 8
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#define TEXT_OFFSET 4
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