Commit 6c826818 authored Jun 12, 2008 by Paul Menage Committed by Linus Torvalds Jun 12, 2008

/proc/sysvipc/shm: fix 32-bit truncation of segment sizes



sysvipc_shm_proc_show() picks between format strings (based on the
expected maximum length of a SHM segment) in a way that prevents gcc from
performing format checks on the seq_printf() parameters.  This hid two
format errors - shp->shm_segsz and shp->shm_nattach are both unsigned
long, but were being printed as unsigned int and signed int respectively.
This leads to 32-bit truncation of SHM segment sizes reported in
/proc/sysvipc/shm.  (And for nattach, but that's less of a problem for
most users).

This patch makes the format string directly visible to gcc's format
specifier checker, and fixes the two broken format specifiers.

Signed-off-by: Paul Menage <menage@google.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent bcf8039e

ipc/shm.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -1058,16 +1058,16 @@ asmlinkage long sys_shmdt(char __user *shmaddr)
		static int sysvipc_shm_proc_show(struct seq_file s, void it)
		{
		struct shmid_kernel *shp = it;
		char *format;

		#define SMALL_STRING "%10d %10d %4o %10u %5u %5u %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
		#define BIG_STRING "%10d %10d %4o %21u %5u %5u %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
		#if BITS_PER_LONG <= 32
		#define SIZE_SPEC "%10lu"
		#else
		#define SIZE_SPEC "%21lu"
		#endif

		if (sizeof(size_t) <= sizeof(int))
		format = SMALL_STRING;
		else
		format = BIG_STRING;
		return seq_printf(s, format,
		return seq_printf(s,
		"%10d %10d %4o " SIZE_SPEC " %5u %5u "
		"%5lu %5u %5u %5u %5u %10lu %10lu %10lu\n",
		shp->shm_perm.key,
		shp->shm_perm.id,
		shp->shm_perm.mode,

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