From 6a6160a7b5c27b3c38651baef92a14fa7072b3c1 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Wed, 14 Jan 2009 14:14:15 +0100 Subject: [CVE-2009-0029] System call wrappers part 13 Signed-off-by: Heiko Carstens --- mm/mlock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index e125156c664e..04d5e7429c55 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -530,7 +530,7 @@ static int do_mlock(unsigned long start, size_t len, int on) return error; } -asmlinkage long sys_mlock(unsigned long start, size_t len) +SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len) { unsigned long locked; unsigned long lock_limit; @@ -558,7 +558,7 @@ asmlinkage long sys_mlock(unsigned long start, size_t len) return error; } -asmlinkage long sys_munlock(unsigned long start, size_t len) +SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) { int ret; -- cgit v1.2.3 From 3480b25743cb7404928d57efeaa3d085708b04c2 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Wed, 14 Jan 2009 14:14:16 +0100 Subject: [CVE-2009-0029] System call wrappers part 14 Signed-off-by: Heiko Carstens --- mm/mlock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index 04d5e7429c55..2904a347e476 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -595,7 +595,7 @@ out: return 0; } -asmlinkage long sys_mlockall(int flags) +SYSCALL_DEFINE1(mlockall, int, flags) { unsigned long lock_limit; int ret = -EINVAL; @@ -623,7 +623,7 @@ out: return ret; } -asmlinkage long sys_munlockall(void) +SYSCALL_DEFINE0(munlockall) { int ret; -- cgit v1.2.3 From 27421e211a39784694b597dbf35848b88363c248 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 1 Feb 2009 11:00:16 -0800 Subject: Manually revert "mlock: downgrade mmap sem while populating mlocked regions" This essentially reverts commit 8edb08caf68184fb170f4f69c7445929e199eaea. It downgraded our mmap semaphore to a read-lock while mlocking pages, in order to allow other threads (and external accesses like "ps" et al) to walk the vma lists and take page faults etc. Which is a nice idea, but the implementation does not work. Because we cannot upgrade the lock back to a write lock without releasing the mmap semaphore, the code had to release the lock entirely and then re-take it as a writelock. However, that meant that the caller possibly lost the vma chain that it was following, since now another thread could come in and mmap/munmap the range. The code tried to work around that by just looking up the vma again and erroring out if that happened, but quite frankly, that was just a buggy hack that doesn't actually protect against anything (the other thread could just have replaced the vma with another one instead of totally unmapping it). The only way to downgrade to a read map _reliably_ is to do it at the end, which is likely the right thing to do: do all the 'vma' operations with the write-lock held, then downgrade to a read after completing them all, and then do the "populate the newly mlocked regions" while holding just the read lock. And then just drop the read-lock and return to user space. The (perhaps somewhat simpler) alternative is to just make all the callers of mlock_vma_pages_range() know that the mmap lock got dropped, and just re-grab the mmap semaphore if it needs to mlock more than one vma region. So we can do this "downgrade mmap sem while populating mlocked regions" thing right, but the way it was done here was absolutely not correct. Thus the revert, in the expectation that we will do it all correctly some day. Cc: Lee Schermerhorn Cc: Rik van Riel Cc: Andrew Morton Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- mm/mlock.c | 47 ++--------------------------------------------- 1 file changed, 2 insertions(+), 45 deletions(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index 2904a347e476..028ec482fdd4 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -294,14 +294,10 @@ static inline int __mlock_posix_error_return(long retval) * * return number of pages [> 0] to be removed from locked_vm on success * of "special" vmas. - * - * return negative error if vma spanning @start-@range disappears while - * mmap semaphore is dropped. Unlikely? */ long mlock_vma_pages_range(struct vm_area_struct *vma, unsigned long start, unsigned long end) { - struct mm_struct *mm = vma->vm_mm; int nr_pages = (end - start) / PAGE_SIZE; BUG_ON(!(vma->vm_flags & VM_LOCKED)); @@ -314,20 +310,8 @@ long mlock_vma_pages_range(struct vm_area_struct *vma, if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) || is_vm_hugetlb_page(vma) || vma == get_gate_vma(current))) { - long error; - downgrade_write(&mm->mmap_sem); - - error = __mlock_vma_pages_range(vma, start, end, 1); - up_read(&mm->mmap_sem); - /* vma can change or disappear */ - down_write(&mm->mmap_sem); - vma = find_vma(mm, start); - /* non-NULL vma must contain @start, but need to check @end */ - if (!vma || end > vma->vm_end) - return -ENOMEM; - - return 0; /* hide other errors from mmap(), et al */ + return __mlock_vma_pages_range(vma, start, end, 1); } /* @@ -438,41 +422,14 @@ success: vma->vm_flags = newflags; if (lock) { - /* - * mmap_sem is currently held for write. Downgrade the write - * lock to a read lock so that other faults, mmap scans, ... - * while we fault in all pages. - */ - downgrade_write(&mm->mmap_sem); - ret = __mlock_vma_pages_range(vma, start, end, 1); - /* - * Need to reacquire mmap sem in write mode, as our callers - * expect this. We have no support for atomically upgrading - * a sem to write, so we need to check for ranges while sem - * is unlocked. - */ - up_read(&mm->mmap_sem); - /* vma can change or disappear */ - down_write(&mm->mmap_sem); - *prev = find_vma(mm, start); - /* non-NULL *prev must contain @start, but need to check @end */ - if (!(*prev) || end > (*prev)->vm_end) - ret = -ENOMEM; - else if (ret > 0) { + if (ret > 0) { mm->locked_vm -= ret; ret = 0; } else ret = __mlock_posix_error_return(ret); /* translate if needed */ } else { - /* - * TODO: for unlocking, pages will already be resident, so - * we don't need to wait for allocations/reclaim/pagein, ... - * However, unlocking a very large region can still take a - * while. Should we downgrade the semaphore for both lock - * AND unlock ? - */ __mlock_vma_pages_range(vma, start, end, 0); } -- cgit v1.2.3 From d5b562330ec766292a3ac54ae5e0673610bd5b3d Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Sun, 8 Feb 2009 20:56:58 +0000 Subject: mm: fix error case in mlock downgrade reversion Commit 27421e211a39784694b597dbf35848b88363c248, Manually revert "mlock: downgrade mmap sem while populating mlocked regions", has introduced its own regression: __mlock_vma_pages_range() may report an error (for example, -EFAULT from trying to lock down pages from beyond EOF), but mlock_vma_pages_range() must hide that from its callers as before. Reported-by: Sami Farin Signed-off-by: Hugh Dickins Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- mm/mlock.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index 028ec482fdd4..037161d61b4e 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -311,7 +311,10 @@ long mlock_vma_pages_range(struct vm_area_struct *vma, is_vm_hugetlb_page(vma) || vma == get_gate_vma(current))) { - return __mlock_vma_pages_range(vma, start, end, 1); + __mlock_vma_pages_range(vma, start, end, 1); + + /* Hide errors from mmap() and other callers */ + return 0; } /* -- cgit v1.2.3 From 9f339e7028e2855717af3193c938f9960ad13b38 Mon Sep 17 00:00:00 2001 From: Markus Metzger Date: Wed, 11 Feb 2009 15:10:27 +0100 Subject: x86, ptrace, mm: fix double-free on race Ptrace_detach() races with __ptrace_unlink() if the traced task is reaped while detaching. This might cause a double-free of the BTS buffer. Change the ptrace_detach() path to only do the memory accounting in ptrace_bts_detach() and leave the buffer free to ptrace_bts_untrace() which will be called from __ptrace_unlink(). The fix follows a proposal from Oleg Nesterov. Reported-by: Oleg Nesterov Signed-off-by: Markus Metzger Signed-off-by: Ingo Molnar --- mm/mlock.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index 028ec482fdd4..2b57f7e60390 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -657,7 +657,7 @@ void *alloc_locked_buffer(size_t size) return buffer; } -void free_locked_buffer(void *buffer, size_t size) +void release_locked_buffer(void *buffer, size_t size) { unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT; @@ -667,6 +667,11 @@ void free_locked_buffer(void *buffer, size_t size) current->mm->locked_vm -= pgsz; up_write(¤t->mm->mmap_sem); +} + +void free_locked_buffer(void *buffer, size_t size) +{ + release_locked_buffer(buffer, size); kfree(buffer); } -- cgit v1.2.3