d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

imgact_elf.c: Add comment explaining the malloc/VOP_UNLOCK() dance

Browse Source 
from r347148.

Requested by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
This commit is contained in:
kib 2019-05-16 13:03:54 +00:00
parent 142b7761cc
commit 27769d9344
1 changed files with 10 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
sys/kern/imgact_elf.c
View File

@ -935,12 +935,22 @@ __elfN(get_interp)(struct image_params *imgp, const Elf_Phdr *phdr,
interp_name_len = phdr->p_filesz;
if (phdr->p_offset > PAGE_SIZE ||
interp_name_len > PAGE_SIZE - phdr->p_offset) {
/*
* The vnode lock might be needed by pagedaemon to
* clean pages owned by the vnode. Do not allow sleep
* waiting for memory with the vnode locked, instead
* try non-sleepable allocation first, and if it
* fails, go to the slow path were we drop the lock
* and do M_WAITOK. Text reference prevents
* modifications of the vnode content.
*/
interp = malloc(interp_name_len + 1, M_TEMP, M_NOWAIT);
if (interp == NULL) {
VOP_UNLOCK(imgp->vp, 0);
interp = malloc(interp_name_len + 1, M_TEMP, M_WAITOK);
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
}
error = vn_rdwr(UIO_READ, imgp->vp, interp,
interp_name_len, phdr->p_offset,
UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred,