Date: Mon, 19 Jun 2017 20:48:01 +0000 (UTC) From: "Kenneth D. Merry" <ken@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r320123 - head/sys/cam/scsi Message-ID: <201706192048.v5JKm1tK034346@repo.freebsd.org>
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Author: ken Date: Mon Jun 19 20:48:00 2017 New Revision: 320123 URL: https://svnweb.freebsd.org/changeset/base/320123 Log: Fix a potential sleep while holding a mutex in the sa(4) driver. If the user issues a MTIOCEXTGET ioctl, and the tape drive in question has a serial number that is longer than 80 characters, we malloc a buffer in saextget() to hold the output of cam_strvis(). Since a mutex is held in that codepath, doing a M_WAITOK malloc could lead to sleeping while holding a mutex. Change it to a M_NOWAIT malloc and bail out if we fail to allocate the memory. Devices with serial numbers longer than 80 bytes are very rare (I don't recall seeing one), so this should be a very unusual case to hit. But it is a bug that should be fixed. sys/cam/scsi/scsi_sa.c: In saextget(), if we need to malloc a buffer to hold the output of cam_strvis(), don't wait for the memory. Fail and return an error if we can't allocate the memory immediately. PR: kern/220094 Submitted by: Jia-Ju Bai <baijiaju1990@163.com> MFC after: 3 days Sponsored by: Spectra Logic Modified: head/sys/cam/scsi/scsi_sa.c Modified: head/sys/cam/scsi/scsi_sa.c ============================================================================== --- head/sys/cam/scsi/scsi_sa.c Mon Jun 19 20:47:24 2017 (r320122) +++ head/sys/cam/scsi/scsi_sa.c Mon Jun 19 20:48:00 2017 (r320123) @@ -4465,7 +4465,18 @@ saextget(struct cdev *dev, struct cam_periph *periph, if (cgd.serial_num_len > sizeof(tmpstr)) { ts2_len = cgd.serial_num_len + 1; ts2_malloc = 1; - tmpstr2 = malloc(ts2_len, M_SCSISA, M_WAITOK | M_ZERO); + tmpstr2 = malloc(ts2_len, M_SCSISA, M_NOWAIT | M_ZERO); + /* + * The 80 characters allocated on the stack above + * will handle the vast majority of serial numbers. + * If we run into one that is larger than that, and + * we can't malloc the length without blocking, + * bail out with an out of memory error. + */ + if (tmpstr2 == NULL) { + error = ENOMEM; + goto extget_bailout; + } } else { ts2_len = sizeof(tmpstr); ts2_malloc = 0;
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