On Wed, 23 Oct 2013 02:50:49 -0400 Naoya Horiguchi <[email protected]> wrote:
> On Wed, Oct 23, 2013 at 02:53:03PM +0900, Akira Takeuchi wrote: > > Hi, > > > > On Wed, 23 Oct 2013 00:26:05 -0400 > > Naoya Horiguchi <[email protected]> wrote: > > > > > Hi, > > > > > > On Wed, Oct 23, 2013 at 11:46:53AM +0900, Akira Takeuchi wrote: > > > > This patch fixes the problem that get_unmapped_area() can return illegal > > > > address and result in failing mmap(2) etc. > > > > > > > > In case that the address higher than PAGE_SIZE is set to > > > > /proc/sys/vm/mmap_min_addr, the address lower than mmap_min_addr can be > > > > returned by get_unmapped_area(), even if you do not pass any virtual > > > > address hint (i.e. the second argument). > > > > > > > > This is because the current get_unmapped_area() code does not take into > > > > account mmap_min_addr. > > > > > > > > This leads to two actual problems as follows: > > > > > > > > 1. mmap(2) can fail with EPERM on the process without CAP_SYS_RAWIO, > > > > although any illegal parameter is not passed. > > > > > > > > 2. The bottom-up search path after the top-down search might not work in > > > > arch_get_unmapped_area_topdown(). > > > > > > > > [How to reproduce] > > > > > > > > --- test.c ------------------------------------------------- > > > > #include <stdio.h> > > > > #include <unistd.h> > > > > #include <sys/mman.h> > > > > #include <sys/errno.h> > > > > > > > > int main(int argc, char *argv[]) > > > > { > > > > void *ret = NULL, *last_map; > > > > size_t pagesize = sysconf(_SC_PAGESIZE); > > > > > > > > do { > > > > last_map = ret; > > > > ret = mmap(0, pagesize, PROT_NONE, > > > > MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); > > > > // printf("ret=%p\n", ret); > > > > } while (ret != MAP_FAILED); > > > > > > > > if (errno != ENOMEM) { > > > > printf("ERR: unexpected errno: %d (last > > > > map=%p)\n", > > > > errno, last_map); > > > > } > > > > > > > > return 0; > > > > } > > > > --------------------------------------------------------------- > > > > > > > > $ gcc -m32 -o test test.c > > > > $ sudo sysctl -w vm.mmap_min_addr=65536 > > > > vm.mmap_min_addr = 65536 > > > > $ ./test (run as non-priviledge user) > > > > ERR: unexpected errno: 1 (last map=0x10000) > > > > > > > > Signed-off-by: Akira Takeuchi <[email protected]> > > > > Signed-off-by: Kiyoshi Owada <[email protected]> > > > > --- > > > > mm/mmap.c | 10 +++++----- > > > > 1 files changed, 5 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > > > index 9d54851..362e5f1 100644 > > > > --- a/mm/mmap.c > > > > +++ b/mm/mmap.c > > > > @@ -1856,7 +1856,7 @@ arch_get_unmapped_area(struct file *filp, > > > > unsigned long addr, > > > > struct vm_area_struct *vma; > > > > struct vm_unmapped_area_info info; > > > > > > > > - if (len > TASK_SIZE) > > > > + if (len > TASK_SIZE - mmap_min_addr) > > > > return -ENOMEM; > > > > > > > > if (flags & MAP_FIXED) > > > > > > I feel that it looks clearer to fix this in round_hint_to_min(), > > > with doing mmap_min_addr check in hint == NULL case. > > > Does it work for you? > > > > The current round_hint_to_min() code checks and adjusts just for > > the hint address, not for "len". Also, it returns no error. > > > > Do you mean adding "len" to the argument of round_hint_to_min() > > and making round_hint_to_min() return any error ? > > I thought of just removing (hint != NULL) check in round_hint_to_min(), > but in my rethinking I found that that affects other code and needs > more changes, so your approach is simpler. I drop my suggestion. > > The above check is to detect too big request, and in your reproducer > len is small (4096), so I'm a bit confused :) > Although it doesn't fix your problem itself, it's correct, I'll add a description as a "Note" to my v2 patch to avoid such confusing. The difference between v1 and v2 patch is only adding the "Note". Thank you for reviewing ! Regadrs, Akira Takeuchi > Reviewed-by: Naoya Horiguchi <[email protected]> > > Thanks, > Naoya Horiguchi > > > > > Regards, > > Akira Takeuchi > > > > > Thanks, > > > Naoya Horiguchi > > > > > > > @@ -1865,7 +1865,7 @@ arch_get_unmapped_area(struct file *filp, > > > > unsigned long addr, > > > > if (addr) { > > > > addr = PAGE_ALIGN(addr); > > > > vma = find_vma(mm, addr); > > > > - if (TASK_SIZE - len >= addr && > > > > + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && > > > > (!vma || addr + len <= vma->vm_start)) > > > > return addr; > > > > } > > > > @@ -1895,7 +1895,7 @@ arch_get_unmapped_area_topdown(struct file *filp, > > > > const unsigned long addr0, > > > > struct vm_unmapped_area_info info; > > > > > > > > /* requested length too big for entire address space */ > > > > - if (len > TASK_SIZE) > > > > + if (len > TASK_SIZE - mmap_min_addr) > > > > return -ENOMEM; > > > > > > > > if (flags & MAP_FIXED) > > > > @@ -1905,14 +1905,14 @@ arch_get_unmapped_area_topdown(struct file > > > > *filp, const unsigned long addr0, > > > > if (addr) { > > > > addr = PAGE_ALIGN(addr); > > > > vma = find_vma(mm, addr); > > > > - if (TASK_SIZE - len >= addr && > > > > + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && > > > > (!vma || addr + len <= vma->vm_start)) > > > > return addr; > > > > } > > > > > > > > info.flags = VM_UNMAPPED_AREA_TOPDOWN; > > > > info.length = len; > > > > - info.low_limit = PAGE_SIZE; > > > > + info.low_limit = max(PAGE_SIZE, mmap_min_addr); > > > > info.high_limit = mm->mmap_base; > > > > info.align_mask = 0; > > > > addr = vm_unmapped_area(&info); > > > > -- > > > > 1.7.0.4 > > > > > > > > > > > > -- > > > > Akira Takeuchi <[email protected]> > > > > > > > > -- > > > > To unsubscribe, send a message with 'unsubscribe linux-mm' in > > > > the body to [email protected]. For more info on Linux MM, > > > > see: http://www.linux-mm.org/ . > > > > Don't email: <a href=mailto:"[email protected]";> [email protected] </a> > > > > > > > > -- > > Akira Takeuchi <[email protected]> > > > > -- > > To unsubscribe, send a message with 'unsubscribe linux-mm' in > > the body to [email protected]. For more info on Linux MM, > > see: http://www.linux-mm.org/ . > > Don't email: <a href=mailto:"[email protected]";> [email protected] </a> > > -- Akira Takeuchi <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
