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[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>
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parent
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commit
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16
fs/select.c
16
fs/select.c
@ -311,7 +311,8 @@ static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
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{
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fd_set_bits fds;
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void *bits;
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int ret, size, max_fdset;
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int ret, max_fdset;
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unsigned int size;
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struct fdtable *fdt;
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/* Allocate small arguments on the stack to save memory and be faster */
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long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
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@ -333,14 +334,15 @@ static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
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* since we used fdset we need to allocate memory in units of
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* long-words.
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*/
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ret = -ENOMEM;
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size = FDS_BYTES(n);
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if (6*size < SELECT_STACK_ALLOC)
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bits = stack_fds;
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else
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bits = stack_fds;
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if (size > sizeof(stack_fds) / 6) {
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/* Not enough space in on-stack array; must use kmalloc */
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ret = -ENOMEM;
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bits = kmalloc(6 * size, GFP_KERNEL);
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if (!bits)
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goto out_nofds;
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if (!bits)
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goto out_nofds;
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}
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fds.in = bits;
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fds.out = bits + size;
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fds.ex = bits + 2*size;
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