Re: [Coverity] Untrusted user data in kernel

[Jan Kasprzak]

: //////////////////////////////////////////////
: // 6:   /drivers/net/wan/sdla.c::sdla_xfer  //
: //////////////////////////////////////////////
: 
	I am not a maintainer of sdla driver, but being Cc'd with this
mail, I'll try to look at it.

: - tainted signed scalar mem.len passed to kmalloc and memset (1206 and
: 1211, or 1220 and 1223). Possibly minor because of kmalloc's
: implicit size check

	Yes. The value mem.len is passed to kmalloc and the code immediately
returns -ENOMEM when kmalloc fails.

: Protected by NET_ADMIN caps, but definately needs some bound checking.
:
	Depends on whether the kmalloc's internal checks are
sufficient or not.

: Jan, I think SDLA_MAX_DATA is the correct bound to check for here, can
: you confirm please?
: 
	I cannot because I don't know or even have this hardware.
However: looking at the definitions in include/linux/sdla.h and the
code itself it looks like SDLA_READMEM, SDLA_WRITEMEM, and SDLA_CLEAR
ioctls are for reading/writing/clearing the card memory itself (maybe
for debugging purposes or downloading a firmware or what). So no,
SDLA_MAX_DATA is probably not a correct limit there.

	The SDLA_CLEAR ioctl (the sdla_clear(dev) function) tries
to clear exactly 65536 bytes (hardcoded at sdla.c:sdla_clear() line 140).
So the mem.len should be <= 65536 bytes, and even mem.addr + mem.len
should be <= 65536 bytes.

	So I propose the following patch (maybe the constant 65536 should
be defined in sdla.h and used both in sdla_xfer() and sdla_clear()):

Signed-off-by: Jan "Yenya" Kasprzak <kas@xxxxxxxxxx>

--- linux-2.4.28/drivers/net/wan/sdla.c.orig	2002-11-29 00:53:14.000000000 +0100
+++ linux-2.4.28/drivers/net/wan/sdla.c	2005-01-06 10:14:21.115490248 +0100
@@ -1195,6 +1195,10 @@
 
 	if(copy_from_user(&mem, info, sizeof(mem)))
 		return -EFAULT;
+
+	if (mem.len <= 0 || mem.addr < 0 || mem.len > 65536 || mem.addr > 65535
+		|| mem.addr + mem.len > 65536)
+		return -EFAULT;
 		
 	if (read)
 	{	


-- 
| Jan "Yenya" Kasprzak  <kas at {fi.muni.cz - work | yenya.net - private}> |
| GPG: ID 1024/D3498839      Fingerprint 0D99A7FB206605D7 8B35FCDE05B18A5E |
| http://www.fi.muni.cz/~kas/   Czech Linux Homepage: http://www.linux.cz/ |
> Whatever the Java applications and desktop dances may lead to, Unix will <
> still be pushing the packets around for a quite a while.      --Rob Pike <
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