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authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>2008-08-05 00:20:05 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2008-08-20 11:15:25 -0700
commita81a91f03af0cb89a8a5144d2bb2dc670000aef8 (patch)
tree2cffc08567f99273b6136c580634e71f7aca17da
parent91e647388fa35ec69e3b3f1b84b2b3f4f4bb15c1 (diff)
downloadlwn-a81a91f03af0cb89a8a5144d2bb2dc670000aef8.tar.gz
lwn-a81a91f03af0cb89a8a5144d2bb2dc670000aef8.zip
mlock() fix return values
commit a477097d9c37c1cf289c7f0257dffcfa42d50197 upstream Halesh says: Please find the below testcase provide to test mlock. Test Case : =========================== #include <sys/resource.h> #include <stdio.h> #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> #include <sys/mman.h> #include <fcntl.h> #include <errno.h> #include <stdlib.h> 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 <halesh.sadashiv@ap.sony.com> Tested-by: Halesh Sadashiv <halesh.sadashiv@ap.sony.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--mm/memory.c16
-rw-r--r--mm/mlock.c2
2 files changed, 13 insertions, 5 deletions
diff --git a/mm/memory.c b/mm/memory.c
index df84668807ad..2d7e6066f7a3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2618,16 +2618,26 @@ 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 7b2656055d6a..01fbe93eff5c 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;
}