From: Al Viro viro@zeniv.linux.org.uk
commit 7780918b36489f0b2f9a3749d7be00c2ceaec513 upstream.
Back in 2.1.29 the clear_user() guts (__bzero()) had been merged with memset(). Unfortunately, while all exception handlers had been copied, one of the exception table entries got lost. As the result, clear_user() starting at 128*n bytes before the end of page and spanning between 8 and 127 bytes into the next page would oops when the second page is unmapped. It's trivial to reproduce - all it takes is
main() { int fd = open("/dev/zero", O_RDONLY); char *p = mmap(NULL, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); munmap(p + 8192, 8192); read(fd, p + 8192 - 128, 192); }
which had been oopsing since March 1997. Says something about the quality of test coverage... ;-/ And while today sparc32 port is nearly dead, back in '97 it had been very much alive; in fact, sparc64 had only been in mainline for 3 months by that point...
Cc: stable@kernel.org Fixes: v2.1.29 Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/sparc/lib/memset.S | 1 + 1 file changed, 1 insertion(+)
--- a/arch/sparc/lib/memset.S +++ b/arch/sparc/lib/memset.S @@ -140,6 +140,7 @@ __bzero: ZERO_LAST_BLOCKS(%o0, 0x48, %g2) ZERO_LAST_BLOCKS(%o0, 0x08, %g2) 13: + EXT(12b, 13b, 21f) be 8f andcc %o1, 4, %g0