From 84d21376c316abf7fd213f30f56781edf8c4e754 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Tue, 5 Aug 2008 00:20:05 +0000 Subject: [PATCH] mlock() fix return values commit a477097d9c37c1cf289c7f0257dffcfa42d50197 upstream Halesh says: Please find the below testcase provide to test mlock. Test Case : =========================== #include #include #include #include #include #include #include #include #include int main(void) { int fd,ret, i = 0; char *addr, *addr1 = NULL; unsigned int page_size; struct rlimit rlim; if (0 != geteuid()) { printf("Execute this pgm as root\n"); exit(1); } /* create a file */ if ((fd = open("mmap_test.c",O_RDWR|O_CREAT,0755)) == -1) { printf("cant create test file\n"); exit(1); } page_size = sysconf(_SC_PAGE_SIZE); /* set the MEMLOCK limit */ rlim.rlim_cur = 2000; rlim.rlim_max = 2000; if ((ret = setrlimit(RLIMIT_MEMLOCK,&rlim)) != 0) { printf("Cant change limit values\n"); exit(1); } addr = 0; while (1) { /* map a page into memory each time*/ if ((addr = (char *) mmap(addr,page_size, PROT_READ | PROT_WRITE,MAP_SHARED,fd,0)) == MAP_FAILED) { printf("cant do mmap on file\n"); exit(1); } if (0 == i) addr1 = addr; i++; errno = 0; /* lock the mapped memory pagewise*/ if ((ret = mlock((char *)addr, 1500)) == -1) { printf("errno value is %d\n", errno); printf("cant lock maped region\n"); exit(1); } addr = addr + page_size; } } ====================================================== This testcase results in an mlock() failure with errno 14 that is EFAULT, but it has nowhere been specified that mlock() will return EFAULT. When I tested the same on older kernels like 2.6.18, I got the correct result i.e errno 12 (ENOMEM). I think in source code mlock(2), setting errno ENOMEM has been missed in do_mlock() , on mlock_fixup() failure. SUSv3 requires the following behavior frmo mlock(2). [ENOMEM] Some or all of the address range specified by the addr and len arguments does not correspond to valid mapped pages in the address space of the process. [EAGAIN] Some or all of the memory identified by the operation could not be locked when the call was made. This rule isn't so nice and slighly strange. but many people think POSIX/SUS compliance is important. Reported-by: Halesh Sadashiv Tested-by: Halesh Sadashiv Signed-off-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 16 +++++++++++++--- mm/mlock.c | 2 -- 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 2302d228fe0..0755c52a817 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2748,16 +2748,26 @@ int make_pages_present(unsigned long addr, unsigned long end) vma = find_vma(current->mm, addr); if (!vma) - return -1; + return -ENOMEM; write = (vma->vm_flags & VM_WRITE) != 0; BUG_ON(addr >= end); BUG_ON(end > vma->vm_end); len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE; ret = get_user_pages(current, current->mm, addr, len, write, 0, NULL, NULL); - if (ret < 0) + if (ret < 0) { + /* + SUS require strange return value to mlock + - invalid addr generate to ENOMEM. + - out of memory should generate EAGAIN. + */ + if (ret == -EFAULT) + ret = -ENOMEM; + else if (ret == -ENOMEM) + ret = -EAGAIN; return ret; - return ret == len ? 0 : -1; + } + return ret == len ? 0 : -ENOMEM; } #if !defined(__HAVE_ARCH_GATE_AREA) diff --git a/mm/mlock.c b/mm/mlock.c index 7b2656055d6..01fbe93eff5 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -78,8 +78,6 @@ success: mm->locked_vm -= pages; out: - if (ret == -ENOMEM) - ret = -EAGAIN; return ret; } -- 2.34.1