diff options
authorThomas Gleixner <tglx@linutronix.de>2017-12-31 11:24:34 +0100
committerIngo Molnar <mingo@kernel.org>2017-12-31 12:14:07 +0100
commita62d69857aab4caa43049e72fe0ed5c4a60518dd (patch)
parentdecab0888e6e14e11d53cefa85f8b3d3b45ce73c (diff)
x86/ldt: Plug memory leak in error path
The error path in write_ldt() tries to free 'old_ldt' instead of the newly allocated 'new_ldt', resulting in a memory leak. It also misses to clean up a half populated LDT pagetable, which is not a leak as it gets cleaned up when the process exits. Free both the potentially half populated LDT pagetable and the newly allocated LDT struct. This can be done unconditionally because once an LDT is mapped subsequent maps will succeed, because the PTE page is already populated and the two LDTs fit into that single page. Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Linus Torvalds <torvalds@linuxfoundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Fixes: f55f0501cbf6 ("x86/pti: Put the LDT in its own PGD if PTI is on") Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1712311121340.1899@nanos Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index 579cc4a66fdf..500e90e44f86 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -421,7 +421,13 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
error = map_ldt_struct(mm, new_ldt, old_ldt ? !old_ldt->slot : 0);
if (error) {
- free_ldt_struct(old_ldt);
+ /*
+ * This only can fail for the first LDT setup. If an LDT is
+ * already installed then the PTE page is already
+ * populated. Mop up a half populated page table.
+ */
+ free_ldt_pgtables(mm);
+ free_ldt_struct(new_ldt);
goto out_unlock;

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