shm: fix null pointer deref when userspace specifies invalid hugepage…

… size Dave reported an oops triggered by trinity: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: newseg+0x10d/0x390 PGD cf8c1067 PUD cf8c2067 PMD 0 Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC CPU: 2 PID: 7636 Comm: trinity-child2 Not tainted 3.9.0+torvalds#67 ... Call Trace: ipcget+0x182/0x380 SyS_shmget+0x5a/0x60 tracesys+0xdd/0xe2 This bug was introduced by commit af73e4d ("hugetlbfs: fix mmap failure in unaligned size request"). Reported-by: Dave Jones <[email protected]> Cc: <[email protected]> Signed-off-by: Li Zefan <[email protected]> Reviewed-by: Naoya Horiguchi <[email protected]> Acked-by: Rik van Riel <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
plbossart · May 9, 2013 · 091d0d5 · 091d0d5
1 parent de2657f
commit 091d0d5
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Showing 2 changed files with 13 additions and 3 deletions.
diff --git a/ipc/shm.c b/ipc/shm.c
@@ -493,7 +493,13 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
 	if (shmflg & SHM_HUGETLB) {
 		struct hstate *hs = hstate_sizelog((shmflg >> SHM_HUGE_SHIFT)
 						& SHM_HUGE_MASK);
-		size_t hugesize = ALIGN(size, huge_page_size(hs));
+		size_t hugesize;
+
+		if (!hs) {
+			error = -EINVAL;
+			goto no_file;
+		}
+		hugesize = ALIGN(size, huge_page_size(hs));
 
 		/* hugetlb_file_setup applies strict accounting */
 		if (shmflg & SHM_NORESERVE)

diff --git a/mm/mmap.c b/mm/mmap.c
@@ -1367,9 +1367,13 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 			len = ALIGN(len, huge_page_size(hstate_file(file)));
 	} else if (flags & MAP_HUGETLB) {
 		struct user_struct *user = NULL;
+		struct hstate *hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) &
+						   SHM_HUGE_MASK);
 
-		len = ALIGN(len, huge_page_size(hstate_sizelog(
-			(flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK)));
+		if (!hs)
+			return -EINVAL;
+
+		len = ALIGN(len, huge_page_size(hs));
 		/*
 		 * VM_NORESERVE is used because the reservations will be
 		 * taken when vm_ops->mmap() is called