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authorSimon Derr <Simon.Derr@bull.net>2005-08-04 19:52:03 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-08-04 21:43:14 -0700
commit2f60f8d3573ff90fe5d75a6d11fd2add1248e7d6 (patch)
tree173980b12459aa55586d3f4f56630abf5af1ffcc
parentb68e9f857271189bd7a59b74c99890de9195b0e1 (diff)
downloadlinux-sh-2f60f8d3573ff90fe5d75a6d11fd2add1248e7d6.tar.gz
[PATCH] __vm_enough_memory() signedness fix
We have found what seems to be a small bug in __vm_enough_memory() when sysctl_overcommit_memory is set to OVERCOMMIT_NEVER. When this bug occurs the systems fails to boot, with /sbin/init whining about fork() returning ENOMEM. We hunted down the problem to this: The deferred update mecanism used in vm_acct_memory(), on a SMP system, allows the vm_committed_space counter to have a negative value. This should not be a problem since this counter is known to be inaccurate. But in __vm_enough_memory() this counter is compared to the `allowed' variable, which is an unsigned long. This comparison is broken since it will consider the negative values of vm_committed_space to be huge positive values, resulting in a memory allocation failure. Signed-off-by: <Jean-Marc.Saffroy@ext.bull.net> Signed-off-by: <Simon.Derr@bull.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--mm/mmap.c6
-rw-r--r--mm/nommu.c6
2 files changed, 10 insertions, 2 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index da3fa90a0aae..404319477e71 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -143,7 +143,11 @@ int __vm_enough_memory(long pages, int cap_sys_admin)
leave 3% of the size of this process for other processes */
allowed -= current->mm->total_vm / 32;
- if (atomic_read(&vm_committed_space) < allowed)
+ /*
+ * cast `allowed' as a signed long because vm_committed_space
+ * sometimes has a negative value
+ */
+ if (atomic_read(&vm_committed_space) < (long)allowed)
return 0;
vm_unacct_memory(pages);
diff --git a/mm/nommu.c b/mm/nommu.c
index ce74452c02d9..fd4e8df0f02d 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1167,7 +1167,11 @@ int __vm_enough_memory(long pages, int cap_sys_admin)
leave 3% of the size of this process for other processes */
allowed -= current->mm->total_vm / 32;
- if (atomic_read(&vm_committed_space) < allowed)
+ /*
+ * cast `allowed' as a signed long because vm_committed_space
+ * sometimes has a negative value
+ */
+ if (atomic_read(&vm_committed_space) < (long)allowed)
return 0;
vm_unacct_memory(pages);