diff options
Diffstat (limited to 'ipc/shm.c')
| -rw-r--r-- | ipc/shm.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index 3174634ca4e5..4982a4e7f009 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -1083,8 +1083,8 @@ out_unlock1: * "raddr" thing points to kernel space, and there has to be a wrapper around * this. */ -long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, - unsigned long shmlba) +long do_shmat(int shmid, char __user *shmaddr, int shmflg, + ulong *raddr, unsigned long shmlba) { struct shmid_kernel *shp; unsigned long addr; @@ -1105,8 +1105,13 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, goto out; else if ((addr = (ulong)shmaddr)) { if (addr & (shmlba - 1)) { - if (shmflg & SHM_RND) - addr &= ~(shmlba - 1); /* round down */ + /* + * Round down to the nearest multiple of shmlba. + * For sane do_mmap_pgoff() parameters, avoid + * round downs that trigger nil-page and MAP_FIXED. + */ + if ((shmflg & SHM_RND) && addr >= shmlba) + addr &= ~(shmlba - 1); else #ifndef __ARCH_FORCE_SHMLBA if (addr & ~PAGE_MASK) |