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Commit 6c826818 authored by Paul Menage's avatar Paul Menage Committed by Linus Torvalds
Browse files

/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: default avatarPaul 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus 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,