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| author |   Mitchell Blank Jr <mitch@sfgoth.com> | 2006-04-10 22:54:08 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@g5.osdl.org> | 2006-04-11 06:18:41 -0700 |
| commit | b04eb6aa08ecc3e24df2f78ebc486011ebd74feb (patch) | |
| tree | 8dbf6a2449f886f0db9c3082dabdf83d4c4f04f7 /fs/select.c | |
| parent | [PATCH] Reinstate const in next_thread() (diff) | |
| download | linux-dev-b04eb6aa08ecc3e24df2f78ebc486011ebd74feb.tar.xz linux-dev-b04eb6aa08ecc3e24df2f78ebc486011ebd74feb.zip | |
[PATCH] select: don't overflow if (SELECT_STACK_ALLOC % sizeof(long) != 0)
If SELECT_STACK_ALLOC is not a multiple of sizeof(long) then stack_fds[]
would be shorter than SELECT_STACK_ALLOC bytes and could overflow later in
the function. Fixed by simply rearranging the test later to work on
sizeof(stack_fds) Currently SELECT_STACK_ALLOC is 256 so this doesn't
happen, but it's nasty to have things like this hidden in the code. What
if later someone decides to change SELECT_STACK_ALLOC to 300?
Signed-off-by: Mitchell Blank Jr <mitch@sfgoth.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/select.c')
| -rw-r--r-- | fs/select.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/fs/select.c b/fs/select.c index fce0fd1bb1d1..a8109baa5e46 100644 --- a/fs/select.c +++ b/fs/select.c @@ -311,7 +311,8 @@ static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, { fd_set_bits fds; void *bits; - int ret, size, max_fdset; + int ret, max_fdset; + unsigned int size; struct fdtable *fdt; /* Allocate small arguments on the stack to save memory and be faster */ long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; @@ -333,14 +334,15 @@ static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, * since we used fdset we need to allocate memory in units of * long-words. */ - ret = -ENOMEM; size = FDS_BYTES(n); - if (6*size < SELECT_STACK_ALLOC) - bits = stack_fds; - else + bits = stack_fds; + if (size > sizeof(stack_fds) / 6) { + /* Not enough space in on-stack array; must use kmalloc */ + ret = -ENOMEM; bits = kmalloc(6 * size, GFP_KERNEL); - if (!bits) - goto out_nofds; + if (!bits) + goto out_nofds; + } fds.in = bits; fds.out = bits + size; fds.ex = bits + 2*size; |