mainlining shenanigans
c7702b8c22
There is a race condition with qla2xxx optrom functions where one thread
might modify optrom buffer, optrom_state while other thread is still
reading from it.
In couple of crashes, it was found that we had successfully passed the
following 'if' check where we confirm optrom_state to be
QLA_SREADING. But by the time we acquired mutex lock to proceed with
memory_read_from_buffer function, some other thread/process had already
modified that option rom buffer and optrom_state from QLA_SREADING to
QLA_SWAITING. Then we got ha->optrom_buffer 0x0 and crashed the system:
if (ha->optrom_state != QLA_SREADING)
return 0;
mutex_lock(&ha->optrom_mutex);
rval = memory_read_from_buffer(buf, count, &off, ha->optrom_buffer,
ha->optrom_region_size);
mutex_unlock(&ha->optrom_mutex);
With current optrom function we get following crash due to a race
condition:
[ 1479.466679] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 1479.466707] IP: [<ffffffff81326756>] memcpy+0x6/0x110
[...]
[ 1479.473673] Call Trace:
[ 1479.474296] [<ffffffff81225cbc>] ? memory_read_from_buffer+0x3c/0x60
[ 1479.474941] [<ffffffffa01574dc>] qla2x00_sysfs_read_optrom+0x9c/0xc0 [qla2xxx]
[ 1479.475571] [<ffffffff8127e76b>] read+0xdb/0x1f0
[ 1479.476206] [<ffffffff811fdf9e>] vfs_read+0x9e/0x170
[ 1479.476839] [<ffffffff811feb6f>] SyS_read+0x7f/0xe0
[ 1479.477466] [<ffffffff816964c9>] system_call_fastpath+0x16/0x1b
Below patch modifies qla2x00_sysfs_read_optrom,
qla2x00_sysfs_write_optrom functions to get the mutex_lock before
checking ha->optrom_state to avoid similar crashes.
The patch was applied and tested and same crashes were no longer
observed again.
Tested-by: Milan P. Gandhi <mgandhi@redhat.com>
Signed-off-by: Milan P. Gandhi <mgandhi@redhat.com>
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.