| Message ID | 20161014092342.25546-2-jslaby@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 14 October 2016 at 11:23, Jiri Slaby <jslaby@suse.cz> wrote: > echo | ./program > where ./program contains fcntl(0, F_SETPIPE_SZ, 0) this is triggered: > UBSAN: Undefined behaviour in ../include/linux/log2.h:63:13 > shift exponent 64 is too large for 64-bit type 'long unsigned int' > CPU: 3 PID: 4978 Comm: syz-executor Not tainted 4.8.1-0-syzkaller #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014 > ... > Call Trace: > ... > [<ffffffffa18ced53>] ? pipe_fcntl+0xa3/0x7a0 > [<ffffffffa18f1940>] ? SyS_fcntl+0x930/0xf30 > [<ffffffffa2d1fb00>] ? entry_SYSCALL_64_fastpath+0x23/0xc1 > > Documentaion of roundup_pow_of_two explicitly mentions that passing > size 0 is undefined. So return 0 from round_pipe_size prematurely to > fix this. > > Signed-off-by: Jiri Slaby <jslaby@suse.cz> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: linux-fsdevel@vger.kernel.org > --- > fs/pipe.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/pipe.c b/fs/pipe.c > index 8e0d9f26dfad..23c0c06ffc33 100644 > --- a/fs/pipe.c > +++ b/fs/pipe.c > @@ -1024,6 +1024,9 @@ static inline unsigned int round_pipe_size(unsigned int size) > { > unsigned long nr_pages; > > + if (!size) > + return 0; > + > nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; > return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; > } Just FYI I sent a patch for this earlier with a bit more analysis, although it probably no longer applies cleanly: https://lkml.org/lkml/2016/8/12/215 Personally I felt it was cleaner to limit the argument passed to round_pipe_size() instead of relying on the implicit long -> int truncation. Anyway, feel free to crib from the patch and/or changelog. Vegard -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/pipe.c b/fs/pipe.c index 8e0d9f26dfad..23c0c06ffc33 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -1024,6 +1024,9 @@ static inline unsigned int round_pipe_size(unsigned int size) { unsigned long nr_pages; + if (!size) + return 0; + nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; return roundup_pow_of_two(nr_pages) << PAGE_SHIFT; }
echo | ./program where ./program contains fcntl(0, F_SETPIPE_SZ, 0) this is triggered: UBSAN: Undefined behaviour in ../include/linux/log2.h:63:13 shift exponent 64 is too large for 64-bit type 'long unsigned int' CPU: 3 PID: 4978 Comm: syz-executor Not tainted 4.8.1-0-syzkaller #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014 ... Call Trace: ... [<ffffffffa18ced53>] ? pipe_fcntl+0xa3/0x7a0 [<ffffffffa18f1940>] ? SyS_fcntl+0x930/0xf30 [<ffffffffa2d1fb00>] ? entry_SYSCALL_64_fastpath+0x23/0xc1 Documentaion of roundup_pow_of_two explicitly mentions that passing size 0 is undefined. So return 0 from round_pipe_size prematurely to fix this. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org --- fs/pipe.c | 3 +++ 1 file changed, 3 insertions(+)